Is a TBC required for converting VHS home videos to digital format?

This is a follow-up question to this one. The DigitalFAQ forum, whose members seem to know a lot about this particular topic, say about TBCs:

You must have some form of TBC, it’s not optional. You can try to scrimp by with an ES10/15 unit, for under £100. It’s minimalist, and not actually a TBC. But if funds matter more than quality, it’s probably the only avenue if really pinching pennies.

What exactly is a TBC, and do I really need one to get decent quality from a VHS capture?