What are Frameworks
Frameworks operate on a system or specific structure that streamlines the creation of something specific. Knit is an example of a game framework that simplifies making games by handling project structure, module organisation and networking for you rather than you having to implement these features yourself.
Beginners should avoid them as they require you to know Luau fairly well. Experienced developers can opt for them though they are entirely optional.
It is recommended to look into frameworks when you want to refactor an existing feature/system, or if you intend to learn more about the feature it implements.