What's the difference between Peak & Mean Velocity?

The fastest rep m/s would be the Peak Velocity & the average would be the Mean Velocity.

Mean Velocity is a measure of the velocity from the start of the concentric lift phase to the end on the concentric phase - GymAware looks at all these points and then takes the mean (average).

Peak Velocity (Max Velocity) is the highest velocity attained during the same concentric lift phase. Its a single point and will always be a much higher number then the mean. The two values do typically correlate well with each other. Thus, if peak velocity increases then so to will the mean velocity) 

It is a graphical trace of bar position v's Velocity for two repetitions. The blue shaded area's are the concentric phase of each rep - this is automatically determined by the software.

The reason we don't use the average term here is because for some higher level metrics we generate .. for example an Athlete does 5 reps, we can look at a single rep mean or peak value or we can look at each rep and get the average of each of these across the whole set. ie average peak velocity (5 reps) average mean velocity (5 reps).