I agree it's confusing, but being an old-timer I've lived through the changes.

COMEX (where gold used to be pit-traded) was taken over by NYMEX in 1994 or 1995.

LIFFE is the London International Financial Futures and Options Exchange. It was also taken-over in multi-mergers and is now part of NYSE Euronext, created when Euronext and the NYSE merged in 2007. It has both London and NY offices.

Different exchanges can always offer futures contracts for the same thing. Gold is an example as is crude oil (managed in London and New York).

And also the old pit-traded commodities have mostly gone to electronic trading now.

The biggest thing to keep in mind is that some of the electronic contracts -- "mini" contracts -- have essentially no trading volume and should be avoided. If you want to trade silver or gold, I suggest the NYMEX contracts (GC - gold and SI - silver) which are available on IB. But both are VERY volatile and are not the best contracts to learn with because you can lose a lot of money fast!

Good Luck!
Chartsky