The live head-to-head tv debate on April 2 featured the leaders of seven parties – Conservative, Labor, UKIP, Liberal-Democrats, Green Party, Plaid Cymru (Wales) and Scottish National Party. (Ken McKay/EPA)

Nearly 50 million Brits are eligible to vote in the nation's first general election in five years, on May 7. But under Britain’s system of parliamentary democracy, it’s not one big election. It’s 650 little elections, with residents of each constituency – an area of around 70,000 citizens -- electing a candidate to represent them in the House of Commons. Whichever party emerges with the most seats will have the best chance of forming a government – at least in theory. (More on that below.)

Here are five questions and answers to help you sort through the vote.

1) What’s at stake?

Quite a bit. The last time Brits voted in a general election, in 2010, the economy was still reeling from the impact of the global financial crisis. Deficits and unemployment rates were way up, and Conservative Party leader David Cameron ran on a pledge to mend the nation’s finances after 13 years of unbroken Labor rule.

Five years of Tory-led coalition government later, Cameron is touting success in halving the deficit and putting two million people back to work, while returning the economy to healthy growth levels and keeping inflation low. His pitch to voters boils down to this: Don’t risk another economic meltdown under Labor. Let me finish the job I’ve started.

Labor leader Ed Miliband counters that the gains of the past five years have been concentrated at the top, and that Cameron has allowed the rich to get away without paying their share even as the poor and the middle class suffer from painful cuts in government services.  He’s pointed to record numbers relying on assistance from food banks as evidence that Cameron’s leadership has failed.

Although Labor hasn’t pledged to roll back austerity measures, the party’s planned cuts are far more modest than the ones being offered by the Tories. Miliband promises a more equitable approach to governing, and a more humane society. Cameron argues that Miliband will run up the government credit card with abandon.

Beyond the economy, health care has been a major issue, with Labor warning that Britain’s revered National Health Service is in peril under Tory rule. Conservatives scoff at those claims.

Foreign policy has barely registered in the campaign, but there is at least one major difference: Cameron says he will give voters a referendum on European Union membership by 2017. Miliband says he won’t.

2) So, who’s going to win?

In a word, nobody. The contest is shaping up as perhaps the most unpredictable in a generation, with Labor and the Conservatives running neck-and-neck. But neither is expected to win a majority, or anything close. That was also true last time around. But last time, the centrist Liberal Democrats won enough seats to put the Tories over the top through a coalition agreement that proved unexpectedly durable. This time, support for the Liberal Democrats has cratered, and neither the math nor the politics favor a simple two-party coalition.

So the parties will have to get creative. Permutations of three or more parties are being actively discussed, though they would inevitably make for strange bedfellows. It’s also possible that one party could try to form a minority government, and hope the other parties don’t band together to bring it crashing down.

Using video posted to YouTube and the hashtag #ChangeTheTune, the U.K.'s Green Party is telling voters that candidates from other parties are all too similar. (YouTube/Green Party of England & Wales)

3) Aside from Labor and the Conservatives, which other parties matter?

The collapse of Labor support in Scotland has provided an opening for the Scottish National Party to become a major player in London. The left-leaning party is forecast to have the third-highest number of parliamentarians after May 7, a remarkable result given the SNP’s stated desire to do away with the UK.

Traditionally, the party with the largest number of parliamentarians gets to govern. But SNP leader Nicola Sturgeon has said that if the Tories are in that spot post-election but fall short of a majority, she’ll throw her support to Miliband and help “lock the Tories out” of 10 Downing Street. In exchange, Miliband will be asked to swallow a good portion of the SNP’s agenda. Other left-leaning parties, including the Greens and the Welsh nationalists, could also enter the mix as part of an informal progressive coalition.

The Tories’ most likely dance partner post-election is their current one: the Liberal Democrats. But after presenting themselves as the fresh alternative in 2010, the Lib Dems’ luster has worn away. They’re likely to lose about half their seats.

The UK Independence Party and its charismatic leader, Nigel Farage, are challenging both the Tories and Labor by appealing to voter anger over mass immigration.  But the party is likely to win far more silver medals than gold, giving it just a handful of seats and a limited ability to influence the next government.

4) Who will be the next British Prime Minister?

When the dust finally settles, one of two men will be prime minister: Cameron or Miliband. And it’s do or die for both men, with the loser likely yielding the leadership of their party to someone else.

Cameron, the 48-year-old leader of the Conservatives, is far more popular than his 45-year-old rival, although the public isn’t exactly smitten with either. According to the pollster YouGov, Cameron’s net approval rating is +1, compared to -26 for Miliband.

Cameron’s supporters say he is effective, efficient and statesmen-like; his critics say he’s out of touch and are apt to point a figure at his elite upbringing.  Miliband is seen as competent, if a bit weird, but also someone who can relate slightly better to the average person than Cameron can.

In Britain, there is no time limit on how long one can serve as prime minister, but Cameron has - some say presumptuously - ruled out running for a third term (before he’s even won a second.).

He recently told the BBC that  “terms are like shredded wheat – two are wonderful but three might just be too many."

5) What’s Queen Elizabeth II’s role in all this?

Queen Elizabeth II is the head of state of the United Kingdom, but she won’t be dashing off to her nearest polling station on May 7th -- as stated on the British monarchy’s web site, the royal family doesn’t vote.

But she is not a regular bystander, either. Once all the ballots have been counted, the queen will summon the leader of the party who wins the majority of the seats in the House of Commons to Buckingham Palace and formally request they form the next government. In the event of a hung Parliament, it is up to the parties to first decide who can command support of the House of Commons. The queen will then endorse that decision.
The monarch’s role in British elections changed in 2011 following the Fixed-term Parliament Act. In the past, the prime minister would ask the queen to dissolve Parliament, but this time round Parliament was dissolved by law on March 30 - the queen didn’t need to be asked. The law removed her discretion to refuse the dissolution of Parliament - even though in practice she had never refused such a request.

Related coverage: 

Britain’s prime minister ate a hot dog with a knife and fork, and it’s a problem

British debate reflects nation’s increasingly fractious politics