What are Hash Tags (#) in Twitter?

What is this – “#” sign doing in a lot of Twitter tweets? Why do most of the webmaster and bloggers use this hash symbol in their tweets?

In simple little words – it’s just categorizing or grouping your tweets like you categorize/group your blog posts in categories.

Here is how Twitter defines it -

"Because Twitter provided no easy way to group tweets or add extra data, the Twitter community came up with their own way: hashtags. A hashtag is similar to other web tags it helps add tweets to a category. Hashtags have the ‘hash’ or ‘pound’ symbol (#) preceding the tag, like so: #traffic, #followfriday, #hashtag.”

Hashtags can be used anywhere in between the tweets, at end or beginning. For example, if you search for #Apple you will get a long list of tweets related to Apple but you will not get any result where tweet says "Apple soon releasing software update to fix iPhone 4 problems" because this tweet is not preceded by hash (#) tag.

Well, there are no rules defined to use these hashtags, you can use them as you want, can create them of your own choice, can add 1-3 tags (or even more) in your tweets. Now you may have understood that not only creating new hashtags will help but even tweeting with some popular hashtags will also increase your followers.