What is the difference between a gamebook and a choose your own adventure?

The difference is mostly scope: 'choose your own adventure' refers to pure choice-based branching stories (and specifically the trademarked book series), while 'gamebook' is the broader term that also includes books with dice, stats, and combat. Every Choose Your Own Adventure book is a gamebook, but not every gamebook is choice-only. Fighting Fantasy, for example, is a gamebook with a full mini role-playing system, whereas the classic CYOA series was choices and endings with no rules. In casual use people treat the terms as interchangeable, and that is fine. If you are writing one, the practical question is not the label but whether you want pure choices or added game mechanics like inventory and health. Both are easy to prototype in a visual builder.