Human Genome Sciences manufactures new lupus drug, Benlysta, in Rockville, Md. (Jeffrey MacMillan/The Washington Post)

In his hour-long State of the Union address Tuesday night, President Obama spent a few seconds announcing a "Precision Medicine Initiative," but did little to explain what he has in mind. Background materials distributed by the White House show that Obama wants to invest in this "innovative field that provides healthcare professionals with tools, knowledge and treatments to tailor care to a person's unique characteristics--such as their genetic makeup."

Here's a primer on "precision medicine," a term you'll doubtless hear more about in years to come.

What is precision medicine?

Clinically, experts don't even agree on a single term for it. But "individualized," "personalized," and "precision," medicine are all used to convey the same idea, according to Gianrico Farrugia, former director of the Mayo Clinic's Center for Individualized Medicine: "rather than treating a person as [part of] a group, treat the person as an individual, based on [his or her] own genetic material, to enable us to provide individualized, personalized and precise care."

On a grander scale, said Keith Yamamoto, vice-chancellor for research at UC San Francisco, precision medicine envisions collecting enormous amounts of information -- not just from humans, but from other species and from basic science research -- and crunching that data to identify ways to diagnose and treat individuals.

What does that mean for me, in a practical sense?

Let's say you have cancer. By analyzing the makeup of a tumor, doctors may be able to better choose which drug to use, rather than employing a hit-and-miss approach based on knowledge of your form of cancer. The use of Tamoxifen for one form of breast cancer is a good example. And they can track the evolution of the tumor over time, to determine whether you need a different drug. If you need medication for another kind of illness, analyzing part of your genome might allow physicians to avoid ineffective or even dangerous drugs that interact poorly with your personal makeup.

All of this followed the completion of the Human Genome Project in 2003. As my colleague Brady Dennis wrote last year: "For reasons scientific and economic, one-size-fits-all blockbuster drugs are giving way to treatments tailored to individuals’ genetic makeups and aimed at narrow subsets of broader diseases."

Other possible applications: alternatives to opioids for pain relief, drugs for specific psychological illnesses, a drug for a small sliver of the people who suffer from cystic fibrosis.

What if I'm healthy? Can precision medicine do anything for me?

If you're planning to have children, genetic testing can reveal their chances of inheriting certain diseases. That's been around for a while. But according to the Web site at UC San Francisco, which hosted a summit on precision medicine in 2013, the hope is that such individualized testing might one day be used to predict, say, whether a woman is likely to develop certain forms of breast cancer or other conditions.

But then you may be confronted with other cost-benefit decisions. If your doctor can tell you with certainty that you'll get Alzheimer's Disease and when onset may begin, would you want to know?

The whole thing sounds really expensive. Is it covered by insurance?

For now, insurance companies are, by and large, agreeing to pay for expensive drugs that target a small number of people. For instance, they are largely covering Kalydeco, a drug for about 4 percent of the estimated 30,000 U.S. cystic fibrosis patients, which costs about $300,000 a year per patient. But they are rebelling at covering the cost of Sovaldi, a new treatment for hepatitis C, which runs about $84,000 for a 12-week treatment -- $1,000 per pill. Even so, pharmaceutical companies increasingly are investing in such medications.

But as such treatments proliferate, many worry that insurance coverage simply won't be able to keep up. For cancer treatment, the most common use of precision medicine, coverage varies by insurance company, Farrugia said.

For predictive care, coverage is rare, he said.

Yamamoto points out that at some point, diagnosing and treating people this way will save money, by eliminating wasteful spending on ineffective tests and treatment.

What is government's role?

Providing money, of course, for everything from research to subsidizing new technology, and testing and approving new drugs. Government also might establish databases for all the information yielded by the millions upon millions of genomic tests and other research. Think of what we might be able to learn when researchers can compare all that information and recognize patterns. And government might be the one place where all those samples can be stored.

Whoa, I don't know whether I want the government to have access to my genetic information.

Privacy and security questions have been raised almost since the beginning of this effort. Experts say they must be worked out if people are to feel comfortable enough to allow the work to proceed.

Related: Obama announces new "Precision Medicine Program"