I would like to purchase some used lego train tracks off ebay. I am not, however, very familiar with the different choices of track systems are out there that I might come across. So I would like to learn more about the existing types of track systems. What kinds has lego used at various eras in their history? Are they inter-changable? If I'd like train tracks that are compatible with the currently available new lego city train sets, what types of tracks should I consider?
If possible, I'd love to see photos of a basic piece of each kind side by side to see the differences.