Most Basils are annuals, although there are some perennial varieties available, but these are less common. It is a tender plant and usually grown in pots on windowsills or in the greenhouse, however they can be planted outside in Britain once the risk of frost has passed (and you can be confident that night time temperatures will remain above 10C)
Start seeds off in pots indoors and either grow on indoors or move outside when the risk of frost has passed. You will need to move them out gradually, preferably acclimatising them in a cold frame or greenhouse first, as the shock of moving them straight out will do them no good at all.
I actually grow basil in the greenhouse in the same grow bags as my tomatoes at the base of the plants. They seem to like similar conditions and they make an excellent growing (and cooking!) companion, and are said to repel whitefly from the tomatoes too.
Grow from seed indoors – they can be grown at any time of year if they are to stay indoors in pots.
Basil has a wide range of uses, and is usually partnered with tomato and mozzarella dishes, used to flavour oils or simply add the leaves to salads.