What is the difference between freighter and passenger plane?

freighter is plane carrying only cargo and BB  with limit DIM, while passenger carrying passenger and stuff on lower deck.

Freighter plan is just to carry cargo and its not allowed to board passengers

While passenger plane can load cargo as well but only in cargo compartments.

Freighter for luggages

Freighter is a plane good for cargo, you can even notice that these kind of planes do not have windows because it carry goods not people.

Passenger plane is the one which transport people and they either be scheduled or charter.

Both Freighter and Passenger Plane we can say that they are operated for commercial reasons.