An else block runs when the if condition is false. I'll show you: if (condition) { path1; } else { path2; } runs exactly one path. You use this when you have two alternatives. If the condition is true, path1 runs.
If the condition is false, path2 runs. One of them always executes. Here's an example: if (score >= 60) { cout << "Pass"; } else { cout << "Fail"; } prints either Pass or Fail, never both, never neither.