Cats spend two thirds of their life sleeping. But they usually sleep only a few hours at a time. They also spend considerable time in "cat napping." This isn't a reference to the length of the naps, but their depths.
Cats can spend hours in a dozy state, alert to changes in their environment. This is often when they spend time near us, even if we are engaged in activities that are not about them.
When cats sleep away from us, they are signaling they want deep, undisturbed, sleep. So this is not a time to pet them and say their name. But when they are sleeping in our activity areas, we can acknowledge them with a chin rub or some sweet talk without disturbing their resting posture. After all, they are hanging with us to get attention. Give them some.
Kittens "cycle faster." Their sleep times, and wake times, are shorter and more numerous. But any cat, of any age, is always either charging, or discharging, their energy. Cat naps are their in-between state which makes them available to us while keeping their energy on tap.
To understand a cat's sleep behavior, we must remember that a cat survives by catching prey. Since they are not the biggest predator on the block, and they hunt alone, the cat must outwit and ambush their prey. Patience is the cat's secret weapon. They have the ability to wait for hours for the right moment; and then explode into blazing action.
So cats have the ability to store up a lot of potential energy, and then unleash it in a few seconds. This is an amazing ability; and requires certain behaviors of the cat.
So they don't have the "run all day" energy type of the dog. They spend of lot of time being ready for quick moves, and quick thinking. That is why cats are successful predators.
They aren't lazy. They are waiting.
Find out more about cat sleeping habits, and how they can mesh with our own.