I have added Tapatalk support to the Forum.
Basically if you are using a smartphone, (i.e iPhone, Android, Blackberry etc) you can have the forum served up in an easy to use way on your phone.
You could always look at the Forum via the Browser on your phone but that doesn't look great on the small screens.
More info can be found here
It generally is a Paid for App, though if you are an Android user you can get it free via GetJar.