Field markings

[SamG]

I don't want to assume...

While watching the recent bowl games (I think they were all at NFL stadium), I noticed additional "hash marks" (for lack of a better term) outside the numbers painted on the field. It looked like a pair on either side of the field.

Now the assumption... do those marks indicate where the 'numbers' would be for a college field?

And just for clarification, when do players need to be "between the numbers"?

Thanks