What's a logo

The other day, my daughter asked me about the little crocodile on the towel in her bathroom. You know: the Lacoste or Izod logo.

Then she asked me what a logo was. Believe it or not, it's difficult to explain what a logo is to a 3.5 year old. Especially when you factor in the subsequent why's that come with the initial answers. Then I realized, most people probably don't know either. This great video by Vox featuring one of my favorite designers, Michael Beirut, sums up pretty well what makes a logo great.