Explain the use of Custom App (_app.js) and Custom Document (_document.js) in Next.js.

Thank you for posing such a nuanced and insightful question. As a frontend developer with a robust background in developing high-performance applications, I've had extensive experience working with Next.js and leveraging its powerful features to build scalable and efficient web applications. To address your question directly, let's dive into the roles and distinctions between the Custom App (_app.js) and Custom Document (_document.js) in a Next.js application. The Custom App feature, defined in the _app.js file, is essentially the backbone of Next.js applications. It serves as the main entry point for initializing pages. The primary purpose of _app.js is to enable global CSS imports, maintain state when navigating between pages, and insert shared components across all pages, such as layouts and navigation bars...