Microsoft 365 Defender = M365 Security
Microsoft Defender for Cloud Apps = MCAS
Microsoft Defender for Endpoints = Defender ATP
Microsoft Defender for Office 365
Microsoft Defender for Identity = Azure ATP
Microsoft Defender for Compliance = Azure Purview
Microsoft Defender for Cloud = Azure Security centre
Microsoft continually promote a name change so if this changes again and renders the above obselete then let us know in the comments below!