What is Government of National Unity
The term "government of national unity" is a term used to refer to a case in which all the major political parties in a country are part of the governing coalition. This type of government occurs in parliamentary systems.
An example of this would be if the two major parties of England combined to form a government. Right now, the Tories are in opposition while Labour is in government. In a national unity government, ministers from each party would be included in the cabinet.
Another term for this is a "grand coalition" government.