Global trading negotiations, such as the round that President Reagan called for at the recent economic summit, are akin to a giant town meeting of the vast majority of the major trading nations of the world.

These talks set the rules that govern world trade. Their main purpose is to establish codes of conduct that allow commerce to flow freely and fairly around the world on the premise that open commerce brings economic growth to everyone.

A global round takes years of negotiations to conclude. The last trade talks, named the Tokyo Round for the site of the negotiations, started in 1973 and were not concluded until six years later, in 1979.

The talks are held under the auspices of the General Agreement on Tariffs and Trade (GATT). There have been six global rounds since GATT was founded by 23 nations in 1948, immediately after World War II, and 90 nations now are members of the GATT. As a result, tariffs on thousand of products have been lowered by all GATT members, affecting a large proportion of trade of its members and spilling over into the trade practices of non-members.

One of GATT's major aims is "the substantial reduction of tariffs and other barriers to trade."

President Reagan, with the support of Japanese Prime Minister Yasuhiro Nakasone, British Prime Minister Margaret Thatcher and West German Chancellor Helmut Kohl, is pushing for another round of trade talks.

But he is facing the strong opposition of French President Francois Mitterrand, who insisted at the economic summit that ended Saturday that any global trade talks should be coupled with talks on currency misalignments in the world, especially the effect of a supercharged dollar on global economies.

One of President Reagan's main goals at the Bonn economic summit was to win the agreement of the other leaders for a 1986 starting date for a new global round.

In addition, many Third World members of GATT, headed by Brazil, oppose a new global round. They fear rules favored by highly developed countries of the West such as the United States will shut them out of the new information revolution and trade in high-technology products -- just as the effects of a largely colonial past kept them from sharing the full fruits of the industrial revolution, in their view.

If the Reagan administration fails to win widespread approval for a new global round, Secretary of State George P. Shultz has warned that the United States will proceed with trade talks on its own, conducting a series of one-on-one talks with trading partners that could lead to separate agreements. Many Europeans see this as the death knell of GATT and the world trading system as it exists today.

In preparation for the global round, the United States is looking toward a series of meetings this year to create a broad consensus on the agenda for the talks, set a definite date for its start and work out its schedule. These preparatory talks include a meeting in Geneva on May 13 and 14 of a group of 18 developed and less-developed nations and a meeting of the GATT Council in June.

The Reagan administration has set ambitious and controversial goals for a new round in an attempt to tip GATT forward to face the trade problems of tomorrow. These include areas never before covered by GATT -- such as trade in services (banking, engineering, architecture and data flows where the United States is considered in the lead), high technology, intellectual property rights and technology transfer.

The United States also wants the agenda to include areas left over from a GATT ministerial meeting in 1982 such as agriculture trade, which could provoke a battle with the United States' allies of Western Europe, especially France, which see its farm subsidies as the glue that holds the European Community together.

In many ways, this new round of trade talks -- which the Economist magazine a year ago termed "the Reagan Round" -- will differ greatly from previous rounds. While the earlier talks dealt mainly with reducing tariffs, which are now at their lowest level in history, the new round will move on to nontariff barriers, which the Reagan administration views as the biggest current impediment to the free flow of world trade.

The last global trade talks, the Tokyo Round, also focused on reducing or eliminating nontariff barriers. They failed, however, to tackle successfully agricultural subsidies -- which remain a controversial subject in Europe.

The previous talks were called the Kennedy Round, after President Kennedy, and ran from 1964 to 1967. That round produced major tariff cuts and an international code against dumping, the selling of goods in another country below their fair market price or the cost of producing them.

That was preceded by the Dillon Round, named for former U.S. Treasury secretary Douglas Dillon, which ran from 1960 to 1961. There were also global trade talks in 1956, 1951, 1949 and 1947.