An ATTiny 44 Datasheet was examined.
What is the difference between a PA pin and a PB pin??
PA stands for Port A 8 and is an 8bit bi-directional I/O port. PB stands for Port B and is a 4 bit bi-directional I/O port. Port B also has the reset pin, and the reset pin has special rules. I don't know how the 4/8 bit distinction is significant.
Individual pins have alternate port functions that can be used as opposed to general digital I/O.
Unused pins should have the internal pull-up enabled.
I looked through the rest of it and couldn't make sense of it other than that it was incredibly detailed about how it operates.