I just recently got into dance improvisation.  It's a whole new world for me.  I understand you know a thing or two about it? 
Improvisation is a free way to express yourself through dance. Artists like Michael Jackson are the epitome of dance improvisers and they love creating new forms of dance/expression. 
It makes sense MJ was a dance improviser.  He was so unique!  How can you tell the difference between normal dance performers and improv dancers?
Improv dancers always try to be unique each time they dance, so you won't see a lot of repetition. But normal performers follow rituals and strict choreography that they practice over and over. 
Fascinating!  Do Improv dancers have any techniques to guide their performance since they don't rely on strict choreography?
Yes they often use feelings, mood, and emotion to guide them to certain movements and techniques. 
Gotcha!  What are some examples of other famous improv dancers?    
Steve Paxton founded Contact Improvisation,[2] a form of dance that utilizes the physical laws of friction, momentum, gravity, and inertia to explore the relationship between dancers.
Never heard of him before.  What else is he known for?  Has he invented a dance style or particular famous for a certain music genre dance performance?
Yes he was a founding member of Grand Union which was formed in 1972 as an experimental dance group.