>>6
They are supposed to be faces.
owo or OwO, the Os are the eyes, they are wide open with surprise. The w is the mouth in a similar shape as in :3, it's a playful smile. It means that you are pleasantly surprised with something, or happy to notice something, etc.
uwu or UwU is similar, but the Us are closed eyelids. The mouth is the same :3 style playful smile. It's like a happily content anime girl who reached satori or something.