Mentions and @replies
Typing @ followed by someone's username anywhere in a post links directly to their profile and lets them know you've mentioned them, via a notification that lands in their Notifications tab.
You can mention as many accounts as you like within a single post, and each one gets tagged and notified independently. To see every post where you've been mentioned by other people, check your Notifications tab, or alternatively search @yourusername directly to pull up a dedicated feed of just those mentions across the whole site. If you'd rather not be mentioned at all by accounts you don't follow — useful if you're getting unwanted attention from strangers — that behavior can be adjusted from your privacy settings, letting you limit who's able to tag you into a conversation in the first place.