TBC Classic servers are home to WOW TBC Gold all the content from Classic and also the content from the TBC expansion. These servers offer the level 70 Outland content as the final game. But, you are able to still play at level 60. It is where classic players are currently.
Blizzard will be launching a new service called "Wow Classic Season of Mastery" within the next few weeks. The servers will provide an exciting new way to play traditional (no TBC content) but with some twists. The twists are things like "leveling can be faster" as well as "raid bosses are difficult to defeat." You should wait a couple of buy WOW Classic TBC Gold weeks to create a character if you only want to play classic content and not about the burning crusade stuff**.