The command, ‘forward-search regexp’, checks each line, starting with the one following the last line listed, for a match for regexp. It lists the line that is found. You can use the synonym, ‘search regexp’, or abbreviate the command name as fo.

reverse-search regexp

The command, ‘reverse-search regexp’, checks each line, starting with the one before the last line listed and going backward, for a match for regexp. It lists the line that is found. You can abbreviate this command as rev.