While loop being weird

[Maygs]

I've written this loop I'm not sure if while was the best way to go about it but anyway... The problem is that it only half works.. If I enter "p" or "c" once it will still execute the while loop. However if I put p or c in a second time it will then return. If I put in anything else it will keep executing the while loop. What is going on here?

void add()
{
	string type;
	cout << "Permanent or Casual? (p/c)" << endl;
	cin >> type;
	while (type != "p" || type != "c"){  //maybe change to for?
		cout << "Invalid type. Please enter either p (permanent) or c (casual)" << endl;
		cin >> type;
		if(type == "p" || type == "c"){
			return;
		}
	}
}

[Maygs]

Okay I changed line 6 to

while (!(type == "p" || type == "c"))

and it seems to be working now. I don't get why this would work but the other way wouldn't but whatever haha.

Edit: I'd love for someone to explain this to me if possible :)

[firedraco]

Think of it like this:

Under what conditions would while (type != "p" || type != "c") be false?

[Maygs]

If type does not equal p or if type does not equal c? :s Hmm it must be obvious but I still can't see the problem I feel silly lol.