Token economies are reinforcement-based strategies that use points, tokens, and chips as reinforcers.

Secondary reinforcers

Primary reinforcers are biological (e.g. food and water), while secondary reinforcers are conditioned (e.g. money, grades, and tokens). 

A token economy is a form of behavior modification, either to increase a desirable behavior or minimize undesirable behaviors with the use of tokens. A token is an object of symbol that is given to a person when they are able to meet certain target behaviors. These tokens can be exchanged or traded for desirable items, services, privileges or activities. The items, services, privileges and activities earned by exchanging the tokens are called back-up reinforcers. 

The diagram below shows the basic flow of a cycle in a token economy (source: http://www.educateautism.com/token-economy.html)