Being a newbie at this myself, before I started last week I took some time to browse the internet and read up on some things I was unsure about..for example...What in the heck is my target heart rate?? Am I excersising too little or overdoing it?? I found this website very helpful....What Is My Target Heart Rate?
This website also has other useful tools that I use and I wanted to post it so that perhaps it may help some of the other "newbies" who may have the same questions.

That's neat - thanks! Some of the machines at the gym have heart rate monitors, I wondered how they come up with the numbers. It's also handy to know what the limit is - not that i have ever been close - but hey..good to know