Kittens meow at their mother for attention and food, but adult cats don’t meow at each other. Female cats will yowl (loudly) when in heat, and male cats will yowl if they sense a female in heat. That’s about the only time adult cats will ‘talk’ to each other. They speak to each other using scent, facial expressions, body language and touch.
Since we humans don’t understand any of that, cats have developed their meows just for us. Most meows are easy for most cat-parents to decipher after a while.
As a guide for newbies:
a short meow or mew: usually a simple greeting (hello!)
multiple meows: a more excited greeting (HI! So good to see you!)
mid-pitch meow: asking for something (food, pats, play)
drawn-out mrrrrooowww: demanding something (I want to go out! NOW!)
low-pitch meow: complaining (Oi! My bowl is empty!)
high-pitch rrrroooowww: anger or pain
growling, spitting, hissing: these are always defensive or aggressive sounds
chittering or bleating: usually when a cat can’t reach prey. Some think that cats make these noises to make their prey curious (before they pounce!)
Your cat may be quiet, or a chatterbox. Sometimes a chatterbox may have you well trained. If your cat knows you’ll respond by feeding or patting them every time they meow, then they’ll take advantage. Most experts agree that the best way to train your cat-kid out of this behaviour is to ignore excessive meowing. Then, when your cat is quiet, reward their silence with food, or pats, or play.
If your cat changes their meowing, it might mean something is wrong. Any noises that your cat makes when doing something that they’d normally do quietly might mean they have a pain, or are ill. Some older cats may suffer from mental confusion as they age, and meow to try to find comfort. The best course is to have your cat checked out if their behaviour changes.