"Cheers", in the UK, means "thanks". It's usually, almost automatically, followed by the word "mate". Phrases like "cheers" and "cheers mate" are incredibly catchy when hearing them hundreds of times a day (especially when said in an English accent), so if you are from the UK or just visiting you won't be able to stop upon arriving elsewhere. Beware! People who aren't used to these phrases will think you are very strange unless you are holding a drink.