what is that #hash symbol

Sometimes you see a tweet using a hash symbol (#) before a few words

The hash mark (#) before a word in a post allows you to tag that post for that word. However, in order to get tracked via a hash tag, you need to opt-in and follow

http://twitter.com/hashtags. Once you’re following Hashtags, every time you make a post in Twitter and tag it with a hash mark like so: #iPhone, it will then show up as a real-time post on http://www.Hashtags.org.

If you then visit Hashtags.org, you can click on any tag and it will show you all of the posts that have been tagged with that keyword.

However, it is possible to view all tweets (posts made to Twitter) that contain a specific tag by modifying your URL a bit like so: http://hashtags.org/tag/iPhone.

You can also subscribe to any updates that contain a tag by posting “follow #tag” (without the quotes) in Twitter.

There is also http://www.hashtweeps.com/ that you can use that makes use of hash marks. This site allows you to see who has been using the hash mark you enter within their posts and how many times they’ve done so. Note that when you visit this site you don’t have to enter the hash symbol (#) in the search box.