Two different lines were executed if the condition was false. Other times, you'll completely ignore the return value, because you're not interested in it. We're using the assignment operator here to place the value 5 in the variable x . However, note that a few of lines down, we are very interested in the return value of an operator. That's how we are able to assign a value to sum .
Operator precedence is covered on the next page.
The other assignment operators are all based on the equals sign, so make sure you understand that before going on. You might guess that it has something to do with addition, and something to do with assignment. It's simply a shortcut. Here's an example of how you might take advantage of this return value. It's not used terribly often, but it can sometimes be useful.