Do I have to use Express in Next.js project?

I’m making a website via Next.js. Next.js provides SSR and dynamic routing.

• Do I have to use Express?
• If so, why do I have to use it?
• What kind of features of Express are useful that are not provided from Next.js?

I think next build & next start show pages as well as I expected.

You do not need to use Express, Next.js already has its own built-in server. However since Express is popular, it is easier for developers to communicate with databases or handle other backend work.