I first heard Matt Thornton of SBGi coin the term and credit should be given to him for pushing this topic at his workshops, on blog and training DVDs. Matt lays out the basic idea on the video below:
Basically there is not a physical endeavour you cannot train in alive fashion, this includes live firearms training and other weapons training. In same cases you may need safety equipment such as simuntion and other training weapons etc.
Some of the main advantages of training in an alive fashion are:
You develop your own game, suited to your body type and you find out what works for you.You are actually training to do what you intend to do during a conflict situation.
You start to develop what I call fighters instincts, and what others call good habits whilst under pressure.
You don't have to base your training on second hand information from others about what works, as you get to experience it first hand, as many times as your need.
You should find your training also becomes a lot more fun and stimulating.
Below is a link to Matt's aliveness blog that contains a lot of great reading:
If you can grasp this principle, you will reach a higher level of performance quicker and learn to problem solve in the moment.