as a noun, 'catch' refers to the act of catching something or the amount of something that has been caught, especially fish. It can also refer to a hidden problem or disadvantage.
'catch' can be used to describe the total number or amount of fish caught. It can also refer to a mechanism for holding something in place, like a latch.
The fishermen were pleased with their catch today.
The catch on the door is broken.
The deal sounds too good to be true; what's the catch?
don't confuse the noun 'catch' (referring to an amount caught or a mechanism) with the action of catching something. The phrase 'What's the catch?' is idiomatic and refers to a hidden problem or disadvantage in a seemingly beneficial situation.
as a verb, 'catch' primarily means to intercept and hold something, especially something that has been thrown, propelled, or is falling. It can also have various other meanings depending on the context, such as to understand (a concept) or to become infected with (an illness).
'catch' can be used in both transitive (with an object) and intransitive (without an object) forms. It has various phrasal verb combinations, like 'catch up,' 'catch on,' and 'catch out.'
Can you catch the ball?
I didn't catch what you said earlier; can you repeat it?
She caught a cold during the winter.
The past tense of 'catch' is 'caught.' Be aware of the various idiomatic uses of 'catch,' such as 'catch someone's eye' (to attract someone's attention) or 'catch some Zs' (to sleep).