There are many different types of illegal gambling, and some gambling activities may be legal in one context but not another. Often, different areas have very different rules about what types of gambling are allowed, sometimes resulting in a concentration of gambling facilities in certain areas. Certain types of gambling may be illegal in an area, or the game must adhere to certain regulations in order to be legal. Illegal gambling often takes the form of otherwise legal games put on in illegal venues, which complicates the issue even further.
One of the most common types of illegal gambling involves games that may otherwise be legal in illegal venues that do not have permission from the state to operate. This may include card games, video poker machines, and even simple games involving coins and dice. Generally, informal games between friends are seen as different than underground gambling rings, but in certain cases even social poker games played for money can be seen as unlawful gambling. When a game is not run with the explicit permission of the government in the form of licenses and other documents, it is generally considered illegal.
Certain types of gambling activities are illegal in many areas no matter who is in control of the venue. For example, cock fighting and dog fighting are often illegal because these games are considered unsafe and cruel to animals. Most games that involve animal death or injury are against the law, but betting on games like bull fighting, dog racing, or horse racing is usually considered a different category of activity.
There are a variety of illegal gambling activities that do not involve playing games but rather predicting the outcome of future events in the public sphere like sports games. Any activity can become a gambling activity of this type, including elections, award shows, and the weather. Sports games are usually considered the most popular because there is an element of chance involved in all games. People who take and give out money for this type of gambling are sometimes called bookies, and in some areas must register with the government in order to be legal.
At different times and in different places, various gambling activities have been against the law. In some areas, all games involving the exchange of money are considered illegal, and in certain religious areas, any activity that resembles gambling even without money involved is questionably legal. Illegal gambling can take nearly any form, so long as money or other resources can be exchanged. Certain types of hidden illegal gambling can be very difficult to catch or identify, but all forms involve financial risk of some sort.