There are several kind of buses: the city bus is called “autobus”, the regional coaches are called “Pullman”.
Ataf buses are the city lines, and cover almost every corner of the city. In the historical centre there are also small electric buses with circular paths (Li-Nea) that can be used with the same ticket of the normal buses.
You can buy the tickets in every newsstand and tobacco shops (see the sign with the “T”) and then validate on bus; the normal ticket costs 1,20 euro and lasts 90 minutes. There are also daily tickets (5 euros), 3 day tickets (12 euros) and “carta agile”, a card with 10 tickets for 10 euros. You can also buy the ticket on the bus (just ask the driver) but the cost is higher (2 euros). The most part of the lines stops at Santa Maria Novella Station and Piazza San Marco.
For the tourists there’s City Sightseeing Tour bus service, with daily tickets and two different lines and multilingual guides that allows you to tour the city seeing the most important tourist attractions and hop on and off to visit what you want. Tickets can be bought on board.
To get out of Florence use the coaches: Lazzi, Sita and Cap. The bus station is right behind Santa Maria Novella Train Station.
To get to Florence Airport you can use the shuttle: departures every 30 minutes from 6.00 to 23.00, the shuttle will take you right in front of Santa Maria Novella Station and back. The single ticket is called "Volainbus" and costs 5 euros, 8 euros if you want the return ticket too.