You're in a meeting. A task comes up. Do you volunteer to do it? Taking on the task is additional work. It is also "sucking up". If you don't want to do something, and then make fun of the people that actually want to get things done and call them names, instead of, y'know, choosing to take on additional work, it's easy to believe that hard work doesn't get you anywhere, because you've chosen to divide things to do at work into "real" work, and "sucking up". There's not really a difference, but in one scenario you think you're better than the other person.
People like it when you do things for them. If you suck up all the work you can do at your job, in my version of corporate America I've experienced, you get promoted.
