Runtime exceptions are a kind of exception that you're not forced to handle. They usually point to serious problems with your code, indicating that you need to revise it. The infamous null pointer exception and array out-of-bounds exception are good examples. Examiners and interviewers love to ask about the two main exception types in Java, so be prepared!
When the video is running, click the maximize button in the lower-right-hand corner to make it full screen.