This question mentions macaron "feet". What are macaron feet?
Take a look at this photo:
The feet are the ruffles on the edges.
A macaron (won't go into the dispute over macaron or macaroon) is a semi-foam/liquid composed of a meringue folded into tant-pour-tant (half and half of icing sugar and ground almonds). When they are baked the top shell layer of the macaron cooks and it means that the macaron can no longer expand and must rise up, this forms a frilled ruffle or foot.