The bars are your best power as w/kg for each duration (5s, 1m, 5m, 60m or optionally 95% of 20m for 3.0). The numbers under each duration are the scale. You can display "category labels" which adds fair, moderate, good, etc. as well as the completely meaningless "cat" labels.

If you have enough history there will be more than 1 bar for each duration, e.g. for each 28 day interval. The number of days is an option that can be changed.

With this chart you can see your improvement (or lack thereof) in each duration over time, as well as the relative "shape" of your power profile. If all of the durations are roughly equal it means you are an all arounder, if the 5s is high and the others fall off, you are a sprinter, and if the FT is the highest and it falls off for the shorter durations, you are more of a a time trialist. Other shapes get more complicated.