Twitter allows its members to easily respond or address each other by placing the “@” symbol in front of the person’s handle (user name), as in @yournamehere in posts. When a post begins with a person’s handle, however, Twitter treats it as a semi-private reply to that person. This means only the sender, the recipient and anybody who happens to follow both people can see the message in their personal Twitter feeds, although the message can also be seen by visiting the sender or recipient’s timeline page.
To convert the message into a form that Twitter will not treat as a personal reply, many users just type a period in front of the handle, as in “.@yournamehere.” If the user name is not at the very beginning of the message, the tweet shows up in the feeds of all the person’s followers because Twitter does not consider it to be an official reply.
Moving the person’s handle even further into the body of the message, as after a salutation (“Hey there, @yournamehere, how do you like those New York Jets now?”) also makes it visible to your followers. Twitter refers to these types of tweets as “mentions” and also lists them on its Connect page for each person noted in the message.