I keep seeing this term: spring rate; what does it mean?

Also, what are progressive rate springs?

Spring rate is the term in pounds required to compress the spring, dual rate springs are just that. They usually contain 2-3 different spring rates on one spring, so the intitial travel can be soft and soak up small bumps at high speed. But when jumping the spring will move into the second rate and be much stiffer, so the chassis does not bottom out landing. There are also setups that use a primary and secondary spring same idea.

cool, very well explained, thanx man