TMP files, also known as temporary files, are used by many computer programs. As the name suggests, these files are created to hold temporary information, usually to retrieve at a later date.
Temporary files can contain any kind of data in any format, and can potentially be used by any computer program ever created, so it's not possible to list all the related applications and tools here. However, if you are trying to find which application created/uses the file, the location of the .tmp file can often provide clues.
As these files can be created by so many different applications, it's not possible to say if these files are safe to delete; as some programs may need the data contained within again whereas other applications may not. If you think it may be safe to delete a .tmp file, make sure you create a backup of the file just-in-case.