Why do people put "#" and a word behind it on FB?

[Chuck]

It's a Twitter mime. Hash tag, as it is called, basically creates a page on Twitter which everyone around the world can share by just adding the same #(whatever the word). So if you add #debtcrisis, there will be a page created called debtcrisis. Now if I were to make a tweet with #debtcrisis it will appear on that page. It is a way of sharing thoughts on world's leading issues.