Forums are a way on MSP to write about anything. You can go from writing about how you feel or what others think you should do or write about a fun little game that provides some humor. You can also create polls. You may see some moviestars put "Forumer" in their status as a sign showing that they are a one who participates in these.
Msp Staff forums
The Moviestarplanet Staff is known to make forums involving important news one in a while. Mods can use this too.