The buses in Barcelona serve all areas of the city, local neighbourhoods but also the main monuments and tourist areas, so visitors can take advantage of the bus network in the city. The bus has improved a lot in Barcelona and now almost all buses have a screen with the name of the next stop, this helps passengers that don't know the are at first sight to get off in the right stop.
Once you get into the bus,you can buy a single ticket directly from the driver, but note that you need to have change, if at all possible coins to buy it. In the bus, right at the entrance there are two machines, one in each side of the corridor to validate your ticket.
It is the passenger responsability to validate the ticket, all the tickets that are a card, if you buy a single ticket from the bus driver you are already validated.
Barcelona bus Lines
The bus lines in Barcelona go around the neighbourhoods, and sometimes in specific areas of the city might be the only option to get there in public transport. The bus network is always in development, new lines come up and different organisation of the city. Check TMB website for all details on the lines and their routes.
Recently, there has been a change of concept in the Barcelona bus lines, there are two different names for the buses: numbers or letter + number.
The new concept of buses, is the letter plus the number, the lines that start with an H run horizontally between Llobregat and Besós rivers. The even numbers indicate that are closest to the mountain or the higher numbers to the sea. For example, the H10 route is closer to the sea than the H8.
There are other lines that start with V, they are vertical lines that go from the sea to the mountains. The odd numbers indicate that they are closer to the Llobregat (V3) or to the Besòs river (V27).
Last but not least, there are lines that start with D, those run the Diagonal Avenue route, from Passeig Marítim until Ernest Lluch. This lines with letter and numbers are colour coded as well, blue for horizontal routes, green for vertical routes and purple for diagonal routes.
The Barcelona urban bus network during daytime is operated by TMB company. The operating hours vary to the type of day, there are some lines for example that do not run on Saturdays or public holidays, check the schedule of the line you want to use online in TMB or in the same bus stop.
During the night, the company who rund the bus service called NitBus, has 17 bus lines that cover the city and the Barcelona surrounding area. All of them, except the N0, go through Plaça de Catalunya, where is the origin of all night lines.
Where to buy bus tickets?
The most common place to buy bus tickets in Barcelona is in a metro station, there are vending machines where you can buy metro and bus tickets, the same type of ticket is valid for either transport, since the company who runs it, TMB is the same. Check the ticket prices from the metro article, since they are shared for bus and metro. You can also buy the tickets in the tourist office, the tmb offices, the tobacco shops or in the ATMs that have servicaixa, but note that they do not sell all the wide variety of integrated tickets, so my recommendation is always to buy it in the metro station