A national flag is a flag that symbolizes a country and that can usually be flown by citizens of that country.
Both public and private buildings such as schools and courthouses often fly the national flag. In some countries, the national flags are only flown from non-military buildings on certain flag days.
There are three distinct types of national flag for use on land, and three for use at sea, although many countries use identical designs for several (and sometimes all) of these types of flag. The three types are civil, state (or governmental), and war (or military) flags. At sea, national flags are called ensigns.