mlocate is a locate/updatedb implementation.  The 'm' stands for "merging":
updatedb reuses the existing database to avoid rereading most of the file
system, which makes updatedb faster and does not trash the system caches as
much.

The locate(1) utility is intended to be completely compatible to slocate.  It
also attempts to be compatible to GNU locate, when it does not conflict with
slocate compatibility.