Please explain Activity Monitor a little bit...

Hi this is part of my Activity Monitor

http://img219.imageshack.us/img219/5568/activitymonitor1.png

What does it mean that tiny apps and applets have such enormous Virtual Memory quantities?

Also I’m not sure if my Macbook is 64 bits, how can I know for sure? And if it isn’t is it still okay that some stuff is running at 64 bits?

That’s all… thanks for any help.