Amount of edgeloops and how to join them

At Creature Factory 03final.flv, at about time 6:30–, Andy has two separate meshes with different amount of edgeloops, then he decides to join the meshes. He adds some edgeloops on the other, and then, suddenly the meshes are all one. What actually happens there? I’ve tried to play it replay, but i cant understand it. Can anyone help me?

It is fairly easy. First he adds the appropriate number of loops using CTRL+R. He then selects the end loops of the upper and lower mesh and presses F and selects skin/face edgeloop from the popup which produces the mesh.

see here: