Buses are often the cheapest way to travel and are usually for short journeys within your local area.
How you pay to travel on them varies between cities so we advise asking your institution. In some places you can buy a ticket from the driver when you board, in others you may have to buy a ticket from a machine before you board the bus. If you pay on the bus, some companies will require you to have the exact fare, others won’t (you will find different bus companies operating in the same city with different rules). In London, you’ll need a ticket in advance, Oyster card or contactless debit or credit card to pay.
The routes of the bus are often posted at every bus stop within the town. Alternatively you can use a travel app like CityMapper. You may also get useful advice from your institution.