Why does rsync create ~ files?

I run the following daily crontab:

rsync -e 'ssh -p xx' -ab --inplace --delete [e-mail]:/home/myname/backup/ /media/internal/myname/backup/

It creates these files:

-rw-r--r-- 1 myname myname 432M Oct  1 00:01 monthly-db-backup.tar.gz
-rw-rw-r-- 1 myname myname 431M Sep  1 00:00 monthly-db-backup.tar.gz~
-rw-r--r-- 1 myname myname   74 Sep 27 10:08 monthly.py
-rw-rw-r-- 1 myname myname   74 Aug 24  2017 monthly.py~
-rw-r--r-- 1 myname myname 1.5M Oct 11 00:00 domain.sql
-rw-r--r-- 1 myname myname 1.5M Oct 10 00:00 domain.sql~
-rwxr--r-- 1 myname myname 8.0K Sep 27 10:18 sessionbackup.db
-rwxrw-r-- 1 myname myname 8.0K Jun  5  2019 sessionbackup.db~

Anyone know why it creates these tilde (~) files? Also anyone know a quick way to delete them?

Answer

Anyone know why it creates these tilde (~) files?

That would be because of the -b option you are specifying to rsync. Its purpose is to request exactly that (creation of backup files for destination files that are being replaced).

Also anyone know a quick way to delete them?

If there is no subdirectory structure to deal with (for example, if you have presented the full list of files), then

rm /path/to/the/directory/*~

would be sufficient. If you need to clean up backup files in subdirectories of that directory, too, then

find /path/to/the/directory -name '*~' -delete

would handle it.