To explore SharePoint web parts effectively, it helps to first understand the foundational concept behind them:
SharePoint Web Parts are modular interface components that define the manner in which information is presented, consumed, and interacted with on a SharePoint page. Microsoft itself describes these as "page building blocks" with the ability to "add text, images, files, video, dynamic content, and more."
SharePoint Web Parts enable administrators, designers, and business users to build intranet pages by integrating dynamic content components, including lists, documents, dashboards, links, conversations, calendars, and built-in data. Web parts are placed on portions of the pages and absorb information on the SharePoint lists, libraries, Microsoft 365 applications, and external systems via APIs or connectors.
The web parts developed today are based on the SharePoint Framework (SPFx), which allows configuring them intuitively, using responsive layouts, and integrating well with the rest of the Microsoft 365 ecosystem. Older ASP.NET technology is the one that is used in classic web parts, and it is more stable but less flexible. Essentially, the web parts make SharePoint more than a mere content storage site, but rather a smart and interactive digital workplace.