flags world nations:

that symbolises a country. The flag is flown by the government, but usually can be flown by citizens of that country as well.
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.
Although the national flag is meant to be a unique symbol for a country, many pairs of countries have highly similar and thus easily confusable flags. Examples include the flags of Monaco and of Indonesia, which differ only slightly in proportion; of the Netherlands and of Luxembourg, which differ in proportion as well as in the shade of blue used; and of Romania and of Chad, which are almost completely identical.