Database overrun with 1000's of "transient" feed, dash, timeouts, etc

I’ve searched for days and seen many other threads and questions regarding this issue around the web and this forum, yet there seems to be no definitive answer or solution or information.

My database is literally overrun with thousands of fields that say things like:

_transient_feed_mod_ (long string of letters/numbers)
_transient_timeout_dash_ (long string of letters/numbers)
_transient_timeout_feed_ (long string of letters/numbers)
_site_transient_timeout_browser_ (long string of letters/numbers)

etc, etc, etc, etc, etc, etc…

Some are indicated as “core functions” and others are not.

Is there anyone, ANYONE, who can tell me (and others) what these thousands of “transient” this and thats that pile up and clog the database are? Are they necessary? Is there any way of “cleaning” them out automatically or not have them mount up at all?

Any information at all would be appreciated.