who?

[John Key]

How do I find out the level of the player and his exp?

[Jelly]

In database ofc

[Mystery]

As Jelly mentioned, the best way to see the player's statistics is through that Database. However, you're able to see additional information in-game by 3 simple commands:

who: "Params: [<name>]\n" "Shows a list of online players and their party and guild."
who2: "Params: [<name>]\n" "Shows a list of online players and their job."
who3: "Params: [<name>]\n" "Shows a list of online players and their location."