This article is from the Recreational Figure Skating FAQ, by Karen Bryden with numerous contributions by others.
At various times throughout these pages, you will notice references to
the skating foot, skating leg, free foot, etc. When you are skating on
one foot, this is your skating foot. The foot which is off the ice is
your free foot. The entire side of the body on the side of the free
foot is the free side, hence the terms, free leg, free arm, etc.
Similar terms apply to the skating side.
You will also note references to LFO, RBI, etc. This is a short-hand
term referring to which edge you are using. The bottom of a skate
blade has two edges, with a concave space between them. The edge
closest to the other skate is your inside edge. The first letter
indicates the skating foot, left or right. The second letter indicates
whether you are skating forward or backward. The third letter
indicates whether you are on an inside or outside edge.