I’ve been seeing this question popping up again and again.

“What is the # sign in front of people’s names on Facebook?” (Also called a “pound symbol” or “sharp sign.”

It’s what’s called a “hash-tag,” and it’s used to “tag” certain topics on the popular social networking website Twitter.

The thing is, Facebook doesn’t support hashtags of that sort, so it might be a little confusing to see them. (It does support hashtags, but more on that later.) If you’re seeing one of your Facebook friends posting a lot of pound signs before people’s names on Facebook, they are probably using an application that automatically keeps their Facebook status in sync with with their Twitter account.

Now, about hash-tags on Facebook. As I said, Facebook does support hashtags, only in a slightly different way. Instead of using the # sign, Facebook uses the @ (or at-sign) for tagging other users. It’s kind of like tagging your friends in photos, only it tags them in a text-based message.

To use tagging on Facebook, just type a “@” when entering your status message – an informational dialog will pop up, and when you then type a friend’s name, that name becomes “clickable” for other users. You friend will also be notified that you mentioned him or her in your status update. Tags are also indexed slightly differently in the Facebook database, so it shows up differently in searches.