In SharePoint, a page is a web page devoted to a particular subject—perhaps a report, a how-to article, a status update, or a specification or schedule. You can customize the layout and look of a page in many ways.
Web parts are the building blocks of your page. Each kind of web part is a container for a certain type of content—text, image, list, chart, and so on. You add web parts to your page, then fill them in with content.
Modern web parts
Complete guide to all modern web parts:
Featured web parts:
Classic web parts