Emacs provides several commands for performing search-and-replace
operations. In addition to the simple M-x replace-string
command, there is M-% (query-replace), which presents
each occurrence of the search pattern and asks you whether to replace
it.
The replace commands normally operate on the text from point to the
end of the buffer. When the region is active, they operate on it
instead (see The Mark and the Region). The basic replace commands replace one
search string (or regexp) with one replacement string. It
is possible to perform several replacements in parallel, using the
command expand-region-abbrevs (see Controlling Abbrev Expansion).