The more voting power a user has, determined by the amount of vested STEEM they own, the more their upvote is worth. So a whale with $45,000+ in vested STEEM (Power Up) can click upvote and you'll receive a lot more than someone with $10 in vested STEEM. If the Owner Ned or Dev Dan or another Top 10 vested STEEM holder upvotes your post, you'll likely earn hundreds to thousands. So be nice to them or you'll never earn a dime. ;)