See also the Bash Configuration page.
Incremental means the search begins before the searcher has finished typing the string to search for. Bash supports this feature with the Incremental Backwards Search (C-r), and the Incremental Forward Search (C-s).
Through repeatedly typing C-r or C-s, older (newer) matching entries are shown and so can be searched through.
There are several posibilities to finish searching:
NB: the amount of 1337'nes increases from top to bottom!
Normally, C-s should activate the Incremental Forward Search. But in nearly every case this leads to a hanging terminal. This comes from stty interpreting C-s as stop-signal.
To recover the terminal from this state, a simple C-q should suffice.