• [help] expands to the text help center (with a link),
• [chat] expands to the text Role-playing Games Chat (with a link),
•  becomes a link to edit the current question, and
• [tour] does nothing at all.
• I had no idea these existed and you have vastly improved my life by informing me that they do. – KRyan Feb 6 '14 at 20:36
• You're most welcome, @KRyan. – TRiG Feb 7 '14 at 10:24