The two tools BlenderGuru used are Even and Flipped. According to the Blender Reference Manual:
Only available for single edge loops. This matches the shape of the edge loop to one of the adjacent edge loops.
When Even is enabled, this flips the target edge loop to match.
Essentially, an edge loop naturally spaces each vertex individually to make it even between its two neighboring vertices (slid, of course, if you want), as pictured below.
Even, however, matches the edge to the profile of one neighboring edge; it determines a definite distance between each vertex on the created loop and a neighboring edge. Flipped matches the profile of the other edge — the one Blender chose not to match the first time.
So BlenderGuru wanted to add an edge loop ( Ctrl + R ) and keep it an even distance from the one edge (for smoothing purposes) so he keyed E , but when Blender selected the wrong edge, he selected the other with F and moved the edge to where he wanted it.