title: What's the difference between "bool" and "bool?"?
body: <p>I use the "bool" type for variables as I was used to in C++, and I try to put the values of functions or properties I expect to be boolean into my variable. However I often encounter cases where the result type is "bool?" and not "bool" and the implicit casting fails.</p>
  
  <p>What is the difference between the two and when is each used? Also, should I use "bool?" as the type for my variable? Is this the best practice?</p>