Next.js has two form of pre-rendering Static Generation and Server-side Rendering. The differente is in when it generates the HTML for a page.

const a = 'Test';
console.log(a);

• Static Generation is the pre-rendering mehos that generates the HTML at build time. The pre-rendering HTML is then reused on each request.
• Server-side Rendering is the pre-rendering method that generates the HTML on each request.

Importantly, Next.js lets you chose wich pre-rendering form to use for each page. You can create a "hybrid" Next.js app using Static Generation for most pages and using Server-side Rendering for others.