He's saying to the hens, "Check out this nice nest over here! This is a good spot to lay your eggs."
Last week all the nest boxes in the coop were taken, so one of my hens was shopping around outside for a nice place to lay an egg. My two roos were right with her, finding a secluded spot and clucking over it, making a scene, enticing her over. I think they checked out 4 places before one of the roos finally led her up into the coop, jumped up into a nest box, somehow got the previous hen to jump out, then he sat in there beside the new hen while she laid her egg.
Also when I put a new nest box in the coop, my head rooster will make a big scene in there to get the girls attention, then if no one gets in, he'll sit in it for a while, demonstrating what a nice nest it is.
Just more fascinating chicken behavior!