As a cat person, I find most explanations of cat behaviour generalised and ingomplete; scientific or not. My Siamese cat yells at me when I have not met my side of our obligations.

Consistency is important for children and animals.

• We get up at sunrise, so he will nuzzle or meow to be let in if he's locked out of my room.
• We get wet food at 7am, and if I'm late he will not be impressed and yell until we are in the kitchen. However, if I'm on time, he will sit on the counter and say a quick meow to let me know he's ready and a good boy.
• He will bring his toys to me when it's time to play, if I don't notice he'll let me know.
• When there's something outside and I come watch he'll look at me and do a little chirp, approving my presence and proud of what he's found
• And when we get home he greets us with the back and forward calling and a nuzzle.

There's much more nonverbal communication than verbal. Everyone knows when their cat is scared or excited, but with a good relationship you can tell when they're anxious or in pain. Cat's know human non-verbal communicotion; they know when you're sad, it just depends on the cat if they'll cuddle or knock you're nick-nacks off a shelf.

Meowing is very common among cats. Go look up videos on YouTube where people attach GoPros to their outdoor cats and see them interact with other cats in the neighborhood.

It can be both. I think it really depends on the specific cat and person. My cat "barks" for needs, "whines" when he loses us, and meows for attention or to get vocalization back. I think attentive cat owners probably know their cat and because it's adaptive behavior it's not the same across the board.

I always interpret it as "I NEED"