An ascending ladder will increase the number of repetitions each round by a specified multiple.
For example, Squats and Burpees ascending in multiples of 2 up to 10 (sometimes listed as 2/4/6/8/10) will go as follows.
Round 1 - 2 Squats, 2 Burpees.
Round 2 - 4 Squats, 4 Burpees.
Round 3 - 6 Squats, 6 Burpees.
Heres an example of a 1/2/3/4/5 ladder of Squats and Burpees in action!
and so on.
A descending ladder is the same, but the reps will decrease each round.