Definition of overlay
When the word "overlay" is used, it is almost always in tournament poker. An overlay occurs when a tournament's cash guarantee is greater than its number of entries. Let's take a simple example to understand this. A tournament is announced. The entry fee is 100??? (forget about the commission fee for now, it is not important for our example). The tournament advertises guaranteed cash prizes of 10,000???. So if 100 players enter the tournament, the tournament organizers will have reached their goal. But if only 80 players enter the tournament, even though the tournament organizers will only have accumulated 8,000???, there will still be 10,000??? in prize money, so an overlay of 2,000???. The gaming room will lose 2000??? and the players will win 2000???.
The overlay hunters
Generally, the most popular poker rooms will have almost no overlay tournaments. The prize money advertised will always be relative to the number of entries. But if you go to some of the lesser known poker rooms, you may find some overlay tournaments. Some tournament players go after these types of tournaments. When you find an overlay tournament, it's like playing a tournament with a higher buy-in, but paying less for the entry.