An intraspecific hybrid is the product of a cross between two members from within the same species.

An interspecific hybrid is the product of a cross between different species within the same genus.

An intergeneric hybrid / bigeneric hybrid is the product of a cross between members of different genera from within the same family.
_______________________

The answer to your second question could be quite complex, depending on the depth you wanted the issue addressed. But yes, chromosome compatibility, or lack thereof, is the major factor.

Oh wow, fabulous explanation there Brandon!

So the intraspecific hybrid is essentially crossing two variants of the same species ((within the same genus))? It would be crossing the species with the/a subspecies of itself then?

Really fascinating. I ought to just get a dummies book of botany, but am not sure where to begin there, lol!

Thanks for taking the time with answering my question- much appreciated!
CMK

"So the intraspecific hybrid is essentially crossing two variants of the same species ((within the same genus))? It would be crossing the species with the/a subspecies of itself then?"

Yes, between two different individuals from within the same species. They could be different cultivars, different varieties, different subspecies, etc.

Thank you Brandon ;-)
CMK