Each member of the Government has an opposite number whose job it is to scrutinise them. If the party in Opposition wins a general election, shadow ministers replace the members of the Government.
So, for example, a shadow Home Office minister would help to deal with home affairs if their party was in Government.
Shadow ministers will present voters with an alternative way of running the country. They will criticise ministers if they disapprove of the work they’re doing.
Senior shadow ministers make up the Shadow Cabinet.