Is it lift or duration on the cam?

[Grinder5]

I see mostly when looking at cams that there are two main ones, if not only two options. The 264 and the 272. What does this number stand for, lift or duration? I would think that duration would be more benefitial for producing power, but most people with say muscle cars get huge lift for that idle sound. So, is it lift or duration?

 

[DSMstatus]

i think its duration, so the valves are open at different and or longer intervels.