Indeed, 'TED', initially, was used to refer to 'T-bill/Eurodollar' spread. However, as time passed, peeps sorta started to use TED to refer to pretty much everything that spread US govt credit on one side to LIBOR.
As to what Eurodollars you trade, it normally involves a strip. For example, if I wanna do 2y notes TED, I would do all the Eurodollar contracts all the way out to Jun 11. Again, it will have to be done in a DV01-weighted fashion.