In C++, parameters are the input values that a function takes in order to perform a task or return a value. Parameters are specified in the function declaration or definition, and are enclosed in parentheses.

Here's an example function that takes two integer parameters:

int add(int a, int b) {
    return a + b;
}

In this function, a and b are the parameters. They are of type int, and they are used to compute the sum of two integers, which is then returned by the function.

When you call this function, you must provide two integers as arguments:

int result = add(2, 3);

In this example, 2 and 3 are the arguments, and they are passed to the add function as the values of a and b, respectively.

You can also have functions with no parameters, or with a variable number of parameters (also known as "variadic functions"). In the case of no parameters, the parentheses are still required, but they are left empty:

void print_hello() {
    std::cout << "Hello, world!" << std::endl;
}

In the case of variadic functions, the parameter list includes an ellipsis (...) to indicate that the function takes a variable number of arguments:

void print_args(int n, ...) {
    va_list args;
    va_start(args, n);
    for (int i = 0; i < n; i++) {
        int arg = va_arg(args, int);
        std::cout << arg << " ";
    }
    va_end(args);
}

In this example, the print_args function takes an integer n and a variable number of integer arguments. The va_list, va_start, and va_end macros are used to iterate over the variable arguments.