About this Mac under the apple menu will tell you system version, type of processor and amout of ram you have installed in your Mac. You also could look in the apple system profiler located in your Utilities folder in your Applications folder. The Apple system profiler will tell you a lot more info than you ever could want to know and is a very handy tool. If you are looking for a utility that tells you how much ram is being used by each application you can open your terminal and type "top" (without quotations).