Tabextensions 3, aka TBE3 is an addon which improves tabbed browsing experiences of Firefox, with various unique features. For example:
- Close multiple tabs by one action (ex. "Close Right Tabs", "Close Left Tabs", and so on.)
- Show a thumbnail, a progress meter, in each tab.
- Move the tab bar from top to left, right, or bottom. The tab bar can be changed from horizontal to vertical.
- Show tabs with indent like a tree.
- Open "View Page Source" and "View Selection Source" in tab.
- ...and so on.
This provides only unique features of old TBE2. You can use each features separately, because, actually the TBE3 is a meta package based on some tiny addons. See the list of addons in the TBE3.
By the way, TBE3 doesn't have some features of TBE2, for example, "colored tabs", "lock/unlock tabs", "session management", etc. If you require them, you should use other additional extensions or the Tab Mix Plus.