How does exactly .ignore() work?

I'm learning C++ from a site and I've studied until this unit : http://ift.tt/2gIYgJe .

I understand this example but I can't understand how .ignore() works ( I don't even understand if it's a proper function or what )

int main()
{
std::cout << "Pick 1 or 2: ";
int choice;
std::cin >> choice;

std::cin.ignore(32767, '\n'); // ignore up to 32767 characters until a \n is removed

std::cout << "Now enter your name: ";
std::string name;
std::getline(std::cin, name);

std::cout << "Hello, " << name << ", you picked " << choice << '\n';

return 0;
}

I tried replacing .ignore(32767, '\n') with .ignore(1, '\n') and .ignore() and it worked just fine aswell . Please enlighten me !