A visa is an official permit to enter the country, which you may need to get if you want to study in England. Students who are not British Citizens or citizens of one of the EU or European Economic Area (EEA) countries may need a visa before travelling to the UK. The visa is placed in the passport or travel document. With a valid UK visa, entry to the UK is normally not refused unless circumstances have changed or false information has been given on application for the visa.
The visa tells the immigration officer at a UK port of arrival: