The avatar is what we call the appearance somebody takes on within the drop-net. Following calibration, each user is given a unique avatar based on their real-world appearance. The user gets to dress their avatar however they want using the default clothing provided, or pay a bit extra for more outfits and finer appearance customization. If you’re the sort of user who uses the drop-net to hang out and be social, some customization is probably a worthwhile investment. If you’re a gamer, though, don’t bother, since games all provide higher levels of avatar customization.
I should mention though that the basic avatar you make for the drop-net does carry over into games and applications to a certain extent. Even if you are playing Mesiterra 2 and you decide to be a gnome, your gnome will still look at least a little bit like your basic avatar. It’s important to give your basic avatar an appearance you are happy with, so you don’t need to edit it more in the future, which can be a little bit confusing and startling for your friends (e.g. “Karen!? Since when were you a 4’10” Japanese high school girl!?)