Can Anyone Give Me Information On Becoming A British Citizen?

I’ve been reading on the UK Border Agency website and so far I have learned that you need to be living in the UK for at least 5 years (or 2 years if your married to a british citizen) to apply for a british citizenship. But it also says that if you are visiting the UK you can only stay for up to six months. So how can you not be a citizen and legally live there for 5 years before you become a citizen? I find it all confusing and I would just like to get information because my mother and I have been talking of maybe me living their after university permanently. This will oubviously not be in the near future but I would like to understand everything so I can think about it and tell my mother. Any information whatsoever would be very helpful.