Check Command
The check command is used to check various pieces of information about the server, the world and the players in it. Some check commands can be used in any world by anybody, but others have restrictions.

Some check commands will give information about the block you are looking at, in these cases blocks like torches and flowers will be considered full size blocks so they might get in the way even if you can see behind them.

/check block will give type, id, data value and coordinates of whatever block you are looking at. If you are looking at a sign it will also show the text on the sign, allowing you to read signs from a great distance.

/check chunk will give you the chunk coordinates of the chunk you are currently in, as well as the region file the chunk is contained in.

/check dir will tell you the direction you are facing in compass, coordinate and yaw format.

/check dist [player] will allow you to check the distance between you and someone else in the same world. By default it cannot be used by noobs, cannot be used in survival worlds and cannot be used if the person is currently hidden from you.

/check id will give you the id (and data value, if applicable) of whatever item is in your hand. You can also do /check id [itemname].

/check ip [player] allows admins to check the ip address of any online player, useful for ip bans.

/check loc will give the coordinates of your current location.

/check look [player] is a staff only command which will point you in the direction of the other player. This command can be blocked by tp privacy.

/check noob will give you a complete list of people in the noob group. This command will be deprecated soon.

/check power will give you redstone power information about whatever block you are looking at.

/check seed allows admins to check the seed of the world they are currently in.

/check spawn will allow you to check the location that you will respawn at when you die.

If you are looking at a mob spawner, /check spawner will tell you what it spawns.

/check stat [stat] will allow you to check various statistics about your account, currently the only choice is /check stat time which will tell you how much time you have spent logged in on the server.

/check time will give you the time of your current world in both a standard time format and the exact integer value of the time.

/check world will give you the name of whatever world you are in.

/check xp will tell you the total amount of experience points you have.