Okay, Twitter is a social networking site in which you can use 140 characters of text to express an opinion on something. Or in the case of my Fraternity, which place has the best hot wings and hotest wait staff, but I digress.
As part of your 140 characters, you use a # to indicate what you are talking about. Example would be something like:
Good job Wayne #NRA.
That is something I "tweeted" after Wayne LaPiere did his interview/response thing a few days back.
Today, after the President's press conference, the # of GunsOverPeople began to garner a lot of "tweets" as people heeded the President's call for people to voice thier opinions on gun control. Shortly after this became a popular twitter posting, pro-gun people began to post with the #GunsOverPeople as well, but with a pro gun bent.
It was good to see that on social media, especially twitter, which is something conservatives, the GOP, and the NRA sometimes lack when attempting to spread the message.