Isearch, that is, incremental search, is the standard way to search in vanilla Emacs. Type ‘C-s’ and start typing a search string – Emacs finds a match to what you’ve typed so far. Change your input, and Emacs adjusts to find the new target. This dynamic, on-the-fly behavior is what is meant by “incremental” search. Regexp Searches (On Beyond Wildcards)Searching with regular expressions (regexps)