tell is used to send private, out-of-character messages to other players. You may also send messages to players on other muds if they are connected to TheLand via Intermud.
If you want to send a message to the player you sent the last message to, you may specify "." as player name. The reply command allows you to answer the last player who messaged you.
Example: @tell foo test @tell . test2
will send both messages to foo.
Note that you can abbreviate the @tell command with "@t".