Salesforce Lightning is a component-based framework and user interface (UI) design system provided by Salesforce.com for building modern and responsive user interfaces for Salesforce applications. It includes Lightning Web Components (LWC), Aura Components, and other UI frameworks for creating custom UI elements, pages, and applications within the Salesforce platform. Lightning Experience is the user interface designed using Salesforce Lightning to provide a consistent and intuitive user experience across devices and browsers.