Functional training does exactly what it says on the tin.
Functional exercises that mimic every day movements or that mirror specific sports and activities are performed in order to increase things like power, strength, speed, success, efficiency and to also help reduce the risk of injury.
The goal is to make an individual's daily activities (whatever they may be) easier to perform.
Many sports people use functional training to improve their ability however it can also be used for people who are new to exercise or who are recovering from serious injuries. It's particularly good for people with specific weaknesses such as bad backs.
The programme will consist primarily of resistance or weight-bearing exercises relevant to the individual's sport or activity.