You have a Microsoft 365 E5 subscription.

https://docs.microsoft.com/en-us/microsoft-365/compliance/sensitivity-labels?view= o365-worldwide

You can use sensitivity labels to: Provide protection settings that include encryption and content markings. For example, apply a " Confidential " label to a document or email, and that label encrypts the content and applies a " Confidential " watermark. Content markings include headers and footers as well as watermarks, and encryption can also restrict what actions authorized people can take on the content. Protect content in Office apps across different platforms and devices. Supported by Word, Excel, PowerPoint, and Outlook on the Office desktop apps and Office on the web. Supported on Windows, macOS, iOS, and Android. Protect content in third-party apps and services by using Microsoft Defender for Cloud Apps. With Defender for Cloud Apps, you can detect, classify, label, and protect content in third-party apps and services, such as SalesForce, Box, or DropBox, even if the third-party app or service does not read or support sensitivity labels.