Good Lawyer Guide's response

A visa is basically a certificate giving written authority of the Government stamped on your passport giving permission to enter another country. Sometimes, the visa is only a port of entry and you will need to talk to an immigration officer about your rights to stay.
There are many different types of visa including visitor visas, unmarried partner, spouse, student and different business visas.

For information about the type of visa you need for your own circumstances, and the information you need to apply for one, contact the Home Office or see an immigration lawyer.