Explain the term "safe seats".

In a simple-pluralistic democracy such as the UK, "safe seats" are generally considered to be constituencies in which the winner of an election is widely considered to be a "foregone conclusion". An example of a safe seat would be Faversham and Mid Kent, where the Conservative Party candidate has won the seat in every election since the constituencies formation with a sizeable majority (17,000 in 2017).
Safe seats are very important factors for voter turnout. Many voters who live in safe seats become apathetic and do not see it necessary to vote, as they consider the election a coronation to the reigning party, instead of being a competitive affair. This creates a system of differential turnout, where some seats in the UK experience exceptionally high turnouts (80% in Winchester) but others experience exceptionally low turnouts (51$ in Wolverhampton South East).