In representative democracies, a mandate (or seat) is the authority granted by a constituency to act as its representative.
Elections, especially ones with a large margin of victory, are often said to give the newly elected government or elected official an implicit mandate to put into effect certain policies. When a government seeks re-election they may introduce new policies as part of the campaign and are hoping for approval from the voters, and say they are seeking a "new mandate". Governments and elected officials may use language of a "mandate" to lend legitimacy to actions that they take in office.
In some languages, a "mandate" can mean a parliamentary seat won in an election rather than the electoral victory itself. In case such a mandate is bound to the wishes of the electorate, it is an imperative mandate, otherwise it is called "free".