What is a counterexample of putting forward false propositions?

The so-called counterexample is an example in which the conditions of the proposition are met, but the conclusion of the proposition is not established.

The existence of such examples is enough to deny the correctness of the proposition. It is enough to determine that this proposition is a false proposition.

Therefore, to deny a proposition, even if you give a counterexample.

For example, this proposition: If a number is even, then it is a composite number. The condition of this proposition is "if a number is even"; The conclusion is "then this number is a composite number"

Now, for example, 2, this number is even, satisfying the condition that it is even. But the conclusion that "this number is a composite number" does not hold, because 2 is not a composite number.

So 2 is the counterexample of this proposition. This counterexample is enough to prove that this proposition is wrong. Is a false proposition

So if a number is even, then it is a composite number. This proposition is false. Although there are no other examples where even numbers are not composite numbers except 2. But a counterexample is enough.