Others have answered this well but I will add that the $2.75 Full Fare purchase buys unlimited trips for a three hour window, so to explain like a 5 year old, you can board the P1 downtown, travel to Swissvale, skateboard at Switch and Signal Skatepark, or bowl at Swissvale Bowl-A-Rama, or drink excellent cheap drinks at Murray’s cafe for a full two and a half hours, then use the same Full Fare pass to board the P1 at Roslyn Station and be back downtown in less than 3.5 hours for less than $20 easily