What is speed shifting?

Speed shifting (No Lift To Shift) is when you shift without letting up on the throttle. Usually you bounce off of the 7500 RPM rev limiter. 

ECMLINK now provides a no lift to shift feature slightly reducing the strain while speed shifting. The rev limiter is lowered to your preset when you push the clutch in instead of bouncing at 7500rpm or higher.

Power shifting is when you shift without letting up on the throttle, and without using the clutch. It can be done, but is very hard on the transmission. Most people who do this become expert transmission rebuilders (or simply broke, or both) in a short period of time. Most Dogbox manufacturers don't even recommend no clutch and recommend a blip of clutch. (cut load for a brief second)