Someone who uploads youtube videos, particularly someone who has some what of a fan base. Although it can mean anyone in youtube, it specifically means someone who makes videos.
Bob uploaded a new video.
Bob is a Youtuber
An over used word meaning taking a picture of your self. This is mainly used by people who are too lazy to say "take a picture of myself" or people who get obsessed with everything that's popular until it gets over used. Selfies are usually posted on Instagram, Facebook, etc.
Sally: What are you doing?
Sarah: Taking selfies with my phone
Sally: Sarah, we are at the movie theater. Will you ever put that thing away?