If you go to the welcome page there is explanation about what they are. Plus the white and blue papers can help as well.
If you still have trouble understanding it, i get it. There is kind of a lot to know.
Many of us here could possibly explain it further if you still are wondering.
Right you are. I've been on Steemit for a month now and somehow that didn't register to me... not sure if that is a take on their UI or my powers of observations :)
I think it has to do with how much research we end up doing to figure the place out makes us just overlook it. Not totally sure.