Other than the fact that Britain describes its immigration documents longer than most (visas are called Permission for Leave to Enter) what else would you need to know about getting into Her Majesty's Service?
Permission for Leave to Remain
Visiting the UK - If you intend to take a short or extended trip to the UK, there are several types of temporary visas which the UK calls Permission for Leave to Enter.
Working in the UK - Just like the student visas, those intending to work in the UK must have employers who are listed in the Tier 2 Registry. Requirements for Working in the UK