Understanding find and replace
Bulk substitution, in three flavours.
Most edits in a long document are repetitive. Find-replace is the lever that turns hours of clicking into seconds.
Plain-text matching.
The default mode looks for a literal string and replaces every occurrence. Special characters in the search term have no meaning — a period is just a period; brackets are literal brackets. This mode is what you want 95% of the time. The only knob worth knowing: case-insensitive vs. case-sensitive matching, which controls whether "Apple" and "apple" are considered the same.
Whole-word matching.
Plain-text matching is greedy with substrings — searching"cat" hits "cat", "category", "truncate", and "caterpillar". Whole-word mode requires a word boundary on each side, so only the word cat matches. Useful when the substring you want to replace coincidentally appears inside other words.
Regex mode.
Regex unlocks pattern-based replacement: capture groups, alternations, character classes, the lot. The replacement string can reference captures with $1, $2, etc. — useful for reformatting (turn (\d4)-(\d2)-(\d2) into $3/$2/$1 to swap ISO dates to slash format). Regex is powerful and easy to misfire — preview before applying, especially with .* or anything unbounded.
Replace all vs. replace one.
This tool replaces every match in one pass — no "next" or "previous" navigation. That's usually what you want for bulk editing. If you need to selectively accept or reject each replacement (as in an IDE's Find & Replace), the right tool is your editor's built-in command, not a batch processor.