Life points are basically your dog's health. Think of it as kind of a video game: after a certain amount of damage, your little character dies.

In your signature, you should see a little thing that says "Character'sName: #/#"
If your dog is a newborn puppy, it would say "#/20"
In that case, # = life points. 20 = total life points.

The higher "#" (not "20" in that case) is, the healthier your dog is. If it says "0/20" your dog is dead. Sorry. xDD If it says "20/20" then your dog is in perfect shape and totally healthy and won't be dying any time soon.

As your dog gets older, the number of total life points it has will decrease. Think of it this way: an old dog can't be perfectly healthy because it's so old, and it's bound to have some problems. However, it can be perfectly healthy for its age.

You can buy both life points and total life points in the store.