Explanation:
Federation is a collection of domains that have established trust. The level of trust may vary, but typically includes authentication and almost always includes authorization. A typical federation might include a number of organizations that have established trust for shared access to a set of resources.
https://docs.microsoft.com/en-us/azure/active-directory/hybrid/whatis-fed

Explanation:
An incident in Microsoft 365 Defender is a collection of correlated alerts and associated data that make up the story of an attack.
https://learn.microsoft.com/es-es/microsoft-365/security/defender/incidents-overview?view=o365-worldwide

The recommended way to enable and use Azure AD Multi-Factor Authentication is with Conditional Access policies. Conditional Access lets you create and define policies that react to sign-in events and that request additional actions before a user is granted access to an application or service.