The "@" symbol is a useful and powerful feature, but use it wisely. Tagging community members on every single post or tagging multiple users at a time is not a good practice.
If you are commenting on a post and want to address your question to a specific person, type the "@" symbol followed by the username of that individual and then select the user you want to tag.
The tagged user will receive a notification that they have been mentioned and it also lets the community know who you are addressing in the thread.
Most users do not know about this feature, but you can save some time when writing a post that refers to a document by typing the "@" symbol followed by the name of the article or post. Select the article or post that you want to reference and it will appear as if it has been linked.
Make sure your post is relevant to the people that you tag, otherwise you may find yourself getting reported to the moderator for inappropriate use of this feature.
Interested in learning more about marking replies as solutions? Read the How to: Accept as solution article.