Temporary file

A temporary file (.TMP) is a file that exists for a short period of time that may contain information while another file is downloading. It could be created by a variety of computer programs for many different purposes. There are many different temporary files, all created for different programs.

$$$
A .$$$ is a file used by many different programs. It is unknown on which specific ones though.

$DB
A .$DB file is a file temporary created while a dBASE database is open. It is used to recover changes if the program crashes unexpectedly.