What are thought errors, why do they happen & why are they a problem?

My understanding is that thought errors are habitual thoughts that aren’t true and create a negative result. For example, “I don’t know enough” or “I’m not connected to other people”. I’ve been having those same thoughts as long as I can remember, and there’s no upside to them.

I think thought errors happen because they are old thoughts that have seemed or can seem true.

Thank you.