Canvas is a tool that allows easy integration of third-party applications within Salesforce, enhancing user experience by enabling access to these applications directly in the Salesforce interface. It provides features like simplified authentication, context services, and cross-domain API calls, making it easier for developers to create integrated applications. Canvas apps can be used in various Salesforce locations, such as Chatter feeds, Visualforce pages, and mobile apps, and require specific user permissions for access and creation.