From the site design perspective, page layout refers to where elements (web parts, images, links, or other content) are located visually. In classic SharePoint sites, this can be achieved using page layouts such as a wiki page, a blog page, or a web part page.
In modern SharePoint, however, the design is much more flexible. The modern SharePoint design framework utilizes a sections-and-columns layout pattern. Pages are divided into areas called sections, and each section can contain up to three columns. Modifying the page layout is as simple as clicking the Edit button when logged in as a site owner and then adding or modifying sections or web parts:
Using the built-in tools to modify page layouts will ensure your site continues to have a responsive design that will look great and perform well on a variety of devices and screens.
You can use the SharePoint Framework to build and deploy client-side web parts using JavaScript. Client-side web parts are built with HTML and JavaScript and can run in both SharePoint Server and SharePoint Online environments. For more information on developing client-side web parts with the SharePoint Framework, see https://docs.microsoft.com/en-us/sharepoint/dev/spfx/web-parts/get-started/build-a-hello-world-web-part.
Next, we'll look at some additional customization options for SharePoint outside the SharePoint product itself.