Liking a Tweet indicates that you appreciate it. You can find all of your likes by clicking the likes tab on your profile.

Tap the heart icon to like a Tweet and the author will see that you appreciate it.

The @ sign is used to call out usernames in Tweets: "Hello @twitter!" People will use your @username to mention you in Tweets, send you a message or link to your profile.

A username is how you're identified on Twitter, and is always preceded immediately by the @ symbol. For instance, Katy Perry is @katyperry.

See "hashtag."

Twitter Alerts enable public safety agencies to inform people during emergencies by highlighting critical time-sensitive content with notifications and a unique look.

Your bio is a short (up to 160 characters) personal description that appears in your profile that serves to characterize your persona on Twitter.

If you block a Twitter user, that account will be unable to follow you or add you to their Twitter lists, and you will not receive a notification if they mention you in a Tweet.

An internal error in our site code and functionality. We find and fix them all the time (nobody's perfect). If you see one, point it out to @Support by sending us a message.

A cashtag is a company ticker symbol preceded by the U.S. dollar sign, e.g. $TWTR. When you click on a cashtag, you'll see other Tweets mentioning that same ticker symbol.