Why do cats sleep all day?

why do cats sleep all day?
why do they never get bored?
does cats understand each other when they speak to each other?

[AppleBr]

Mines sleep all day long to save energy for the late hours :-)
Cats are nocturne animals, you know...
And probably they ( cats in general) get bored when we try to wake up them to play in not appropriated hours
Guess they really understand each other cos when one of my "granddaughters" mews mother cat cames running to check it out.

[margypops]

Mine doesn't she is in and out all morning sleeps a few hours in the afternoon then is out around 5pm till about 7pm then in all night.When the clocks go back next week she will be inside earlier.I think cats do get bored or sad and that's why they sleep all day , what else do they have to do ..unless they are cats that like playing with toys a lot and some do .

[LivingInHope]

My cat does not sleep all day.  I believe as cats get older, they sleep more.  She does take frequent cat naps, but can open her eyes quickly and often seems to know when she is being talked about.  Sometimes, she goes into a deeper sleep where she has cat dreams and her little whiskers can quiver.  She spend a lot of time grooming, some time exploring, basks in massages and scratching from her guardians, and some times, gets on her hind legs and paws at me at the computer chair or knocks with a front paw at my sister's door when she is hungry and wants to eat.  

Cats can have pent up energy and my cat likes to play.  Sometimes, she tries to get me to play with her and sometimes she goes down to the basement and plays by herself, then tears up the stairs like a house a fire.  Sometimes, I think she is bored when she wants to eat so early.  Sometimes I think boredom can lead to overgrooming.  She is interested in following me around quite often.

Cats have certain behavior that other cats can understand.  They take certain positions which communicate messages.  Also, one can hiss at another, like a neighbor's cat did at another cat we feed snacks to at our back door (like this is my territory and I get snacks here, stay away).  I imagine they understand certain meows at each other, since being meowbal (not verbal like humans) is the language of cats, right?

[margypops]

I have also noticed they are very territorial mine really spits and hisses at any that come by, I haven't seen her attack any but she runs up to them and hisses threateningly,she doesn't like me giving any food, I have to do it when she's not there if they come by so she is jealous..She hates rain I guess most cats do ..and its raining today so she has been out twice and got wet but she gives me dirty looks like I invented rain ...