it's a twitter thing...if you don't understand twitter you really won't get the 'hashtag' thing, but simply put its a way to link to a twitter account, much like using the @ on facebook links or tags a facebook user in a facebook post. using the hashtag allows for categorization of twitter thoughts, for example #richardsherman would have allowed twitter to rank how many people are talking about richard sherman if they used the string #richardsherman....simply a way that twitter was able to monetize the use of twitter to those that are using it for social relevancy or revenue streams or just plain ego