Client-Side Web Parts (CSWP) are a modern approach to creating and deploying web parts in SharePoint Online and SharePoint Framework (SPFx). These web parts leverage client-side technologies and provide a more responsive user experience compared to traditional server-side web parts.
Client-Side Web Parts represent the future of web part development in SharePoint, aligning with modern web development practices and providing a robust platform for building rich, interactive, and engaging SharePoint applications.