These operate on а тало́н paper ticket system. You'll purchase a кни́жечка booklet of 10 tickets from the води́тель driver, or at а кио́ск. You'll tear off a single ticket and validate it for every trip you make. There are no transfers, and a validated ticket is good only for one trip.

Buses and trolleybuses have multiple doors and it is common practice to board through the back door and exit from the front. Don't be surprised, however, to see this "etiquette" often ignored.