I made the same question when I started and people encouraged me to investigate it. I just leaved it apart:-P and I discovered it just some weeks ago.
They are state Tiddlers. Any widget that needs a temporary unique place to store information creates that kind of Tiddlers. You can freeley remove them
In my opinion it would be better if they are not treated as regular Tiddlers.
Regards.
will they affect performance if there are a ton of them?
<<tabs "[[filter expession]]" "default tab" "Target-tiddler!!target-field">>