A short meow is a basic greeting or request for attention from cats to humans. They seek acknowledgment.
Drawn out meows communicate urgency about something. Your cat likely wants food, help accessing a space, or attention.
A frustrated cat may emit a fast chattering meow. Something they want is out of reach, like a bird in the yard.
Purring signals contentment. But cats also purr to comfort themselves when nervous, so context is important.
Trills combined with squinty eyes are indicative of happiness in cats. It often means they like something you're doing.
Chirps are friendly vocalizations cats use during greetings. Squeaks are higher pitched chirps when very excited.
Chirps & Squeaks
Growling and hissing expresses irritation, overstimulation, fear or confrontation. Leave an agitated cat alone.
Growling & Hissing