A texting emoticon
furries and weebs (for some reason) use.
Furries usually use "OwO" in a sexual and/or curious way, but mostly as a joke; and usually type messages like this: "OwO what's this?" Weebs use the "OwO" emote to seem quirky and kawaii.
Furries are the ones to get confused when anime fans use an emote they themselves made up.