If you're on basic rate, it means that all of your income from a certain source is being taxed at the basic rate of 22% (with no tax free pay). This usually happens in "second job" situations, where your earnings are over the personal allowance and starting rate tax levels in your "first" job(currently the standard personal allowance is �90-ish per week/�4749 per year).
The other rates of tax are starting rate (10%) on the first �2000-ish you earn over the personal allowance in a year, then basic rate is deducted on earnings between this and �30000-ish and if you're lucky enough to have earnings over that level, you'll pay 40% tax on the rest.