To bump a question means you think the question deserves more answers.
To vote up an answer means you like their answer, agree with them, the answer is funny, etc.
But basically, you earn basic credits by asking questions, answering questions, bumping questions and voting up answers. You get a certain amount of each of those a day so you cant go crazy asking tons of questions a day just to earn points.
You also earn extra credit by being voted best answer, by getting your question bumped and by getting your answer voted up.
The credits are so you can unlock things such as anonymous for answering questions and also to down vote.
You can also lose credits for having your answer get down voted or deleting a question or answer or reporting someone.
I think thats everything in a nutshell :)
at 5:36 PM on Jul. 7, 2010