PCINT0, PCINT1, PCINT2, etc. on ATtiny45/85
That is simply the difference between an external interrupt INTx and a pin change interrupt PCINT. The first is an interrupt for a single pin. The second is an interrupt for a complete group of pins. Normally this group is a complete port. As the Attiny85 only has one port, this is the case here. So the whole group is only 1 single interrupt source. Thus it only has one interrupt vector named PCINT0_vect.

A pin change interrupt triggers, when any of the pins under it's supervision changes. You can remove pins from it's supervision by masking them with the PCMSK register.

So the interrupt vector PCINT_vect will be triggered by every change on any of the pins, that are not masked out. It is up to you to check, which one changed it's level.



On bigger microcontrollers, there are more pins and mostly also most of them are connected to a pin change interrupt. Here mostly every complete port is connected to a single pin change interrupt. Thus the corresponding registers are additionally marked with a number (PCINT0_vect as the interrupt vector for the first port, ...)