A slot is a set of resources (processors, memory, etc.) that can be accessed by one or more functional units (FUs). In very long instruction word (VLIW) computers, the term slot also refers to the machinery that issues and executes operations in a single machine.
Many people who play slots do so with the hope of winning big, but it is important to remember that luck plays a major role in slot success. It is also important to choose machines that appeal to you. Some machines may pay more than others, but if you do not enjoy the games you are playing, you will be less likely to return to them in the future.