I had to go for heart tests today and am wondering what they can tell from me go!

I had to go for heart tests today and am wondering what they can tell from me going on the walking machine?

Sorry that machine has a name but I just can't think of it now....old age!

As pointed out, it's called a stress test. It's an important test to run because a lot of tests only show results from your cardiac activity while at rest. Even when you get an EKG taken, you are asked to stay very still.
A stress test will show your doctor how your heart reacts in stressful conditions...a very important side of how your heart reacts and what could possibly trigger a cardiac episode.
It measures your BPM (beats per minute) in regards to how much physical stress you are being exposed to and it also shows the activity of the parts of the heart to make sure they are reacting accordingly with the rest of your heart.
This is one of the most important heart tests to have as most cardiac events (arrythmias, cardiac arrest) occur when you're under physical stress. If your heart works well under these conditions, it's a pretty good sign that your heart is healthy and it's OK for you to push yourself during exercise or physical work. It's a very common test, especially as you get older to make sure that you're healthy enough to start certain exercise regimines and a good measure to see how your health is overall as you age.