I had the same question when I first looked at it. Have no idea what it is, and I am not sure what CAP is either.
However, when I looked at the chart I figured it is not really that good of a chart at all. For example, limping pre-flop in 6-max is suicidal especially from UTG, so for example A2s-A8s is not a call IMO, either bet and put pressure or fold.
Same goes for ATo, which is also never a limp from UTG but always a bet..
Maybe it's just my play style, and the chart is actually good... Would be cool to know who created it to ask all this directly!
p.s. welcome to CC