What does it mean when a cat is practicing making biscuits?

When they're kittens, they push their paws against their mother's belly to get the milk flowing. They basically knead their mother's belly like it's bread dough. Most cats continue to do this kneading -- they'll knead blankets, people, etc. -- for the rest of their lives. Even very old cats do it. Apparently it is some kind of regression behavior. So, when a cat is practicing making biscuits, I guess it means the cat is thinking about his/her mommy.