C++ :: Char Arrays - Getting User Input Through Different Methods

I've been experimenting with char arrays and getting user input through different methods.

int main() {
char userInput[21];
/*I understand that over here, a maximum of 20 letters can be input, and only letters before a space will be stored in userInput*/
std::cin >> userInput;
std::cout << userInput << std::endl;

[Code] ....

As I was testing, whenever I would input a single word for userInput (for example "hi"), the program would work as expected: it would output "hi" and I'd be able to input a sentence of sorts for userInput2 (for example "hello world") and have it outputted.

But if I were to input more than one word for user Input (for example "hi how are you"), the program would output "hi" as expected, but it wouldn't let me input anything for userInput2 and would just output the rest of the first input; in this case, "how are you" would be outputted and the program would end. I am not aware of the logic error at play.