From a certain approach the term state flags has two distinct meanings. These are the flags of a state/government and the flag of an individual subnational state. Regarding the government flags first of all, you should know that these state flags are variants of national flags (or, occasionally, completely different designs/patterns). The state flags are specifically designated and restricted through law or custom, either theoretically or in fact, to be used only by a state’s government or its agencies. And this is why they are sometimes referred to as government flags, as well.
Although in many countries the state flags and the civil flags – those flown by the general public, are the same, there are countries in which the state flags are more complex variants of national flags. This situation can be encountered especially in Latin American countries as well as in central Europe and in Scandinavia. These state flags often feature the national coats of arms or other emblems as part of their design. An extra way to differentiate state flags from civil flags, in Scandinavian countries, is the use of swallow-tailed flags; some countries have state ensigns, separate flags to be used by non-military government ships like coast guard vessels.
Another aspect to know about is that state flags should not be confused with the national flags as they are used by military organisations. These are referred to as naval ensigns and war flags. Here are some of the states/countries whose flags come in separate state flags and civil flags: Argentina, Austria, Belgium, Bolivia, Chile, Costa rica, Denmark, Dominican Republic, Ecuador, El Salvador, Finland, Germany, Guatemala, Haiti, Iceland, India, Lichtenstein, Lithuania, Monaco, Norway, Peru, San Marino, Serbia, Spain, Sweden, Venezuela etc.
Now, let us not forget the United States, Australia and other federal countries where the term state flags can have a different usage. In such cases, state flags frequently refer to official flags of the individual states or territorial sub-divisions which form the nation. In order for confusions to be avoided it is advisable for these state flags to be referred to as „the flag of the state of X”. The flags of the US present a huge variety of regional/local influences as well as histories. They are also different in style and design principles.
Modern state flags date back to the 1890s when, at the 1893 World's Columbian Exposition in Chicago, the states expressed their wish to have distinctive symbols. Most American state flags were designed and adopted between 1893 and the Second World War and, according to a 2001 survey by the North American Vexillological Association, New Mexico has the best-designed flag of any U.S. state, U.S. territory, or Canadian province, whereas Georgia's 2001–2003 state flag was rated the worst indesign. The state flags are a wonderful modality to express your love and respect for the place of your origin.