What (if anything) is the default functionality of the Tab key in Vim?

Question

I have been using Vim for a while, and it seemed strange to me that an editor with such a focus on reducing keystrokes would leave a large, easily accessible key, such as Tab unbound.

It's huge, it's right under my left little finger, and it just sits there. I feel a little silly even asking this question, but I feel that something is missing.

Is there some reason <Tab> is left without a predetermined goal in both normal and visual modes - maybe some backward compatibility or an edge case that I don't know about? Should I just go ahead and use it in my own Vim configuration without fear or is this a bad idea?

Answer 1

Tab and CTRL-I are the same in Vim, and it was used to go through the jump list (opposite CTRL-O).

From the documentation ( :help <tab> ):

 <Tab> or *CTRL-I* *<Tab>* CTRL-I Go to [count] newer cursor position in jump list (not a motion command). In a |quickfix-window| it takes you to the position of the error under the cursor. {not in Vi} {not available without the |+jumplist| feature}