Question: I am editing questions for better understanding. However, for an approved edit, I get 2 Reputation points. On Rejection, I get 0 points, with reason. Recently, I have successfully edited one question, this is the link: <https://stackoverflow.com/questions/8784757/unable-to-run-new-project-after-updating-the-eclipse-and-adtold-proj-are-runnin> 

It is showing that I have edited the question, but I haven't received any reputation points for it. What is the reason for not getting reputation points for successful editing?

Answer: 
User called `Java` edited the code sample, see [this suggested edit](https://stackoverflow.com/suggested-edits/175885).

By retagging the question, you actually Approved his suggested edit and added your own edit, which was the tags edit.

When you'll have 2K+ rep you'll see it's called "Improve". :)

Another option for what happened is that you really edited the code adding formatting plus edited the tags, but the other user also edited the code and the two edits were merged.
You have enough reputation to [retag questions](https://stackoverflow.com/privileges/retag-questions). Retags do not go through an approval process and therefore do not earn you any additional reputation. Only edit suggestions that change content along with tags will earn you reputation when approved.