Apple will warn users if they appear to be followed by others with tracking devices. For example, if you're at an airport walking along with a crowd of people. If someone else in the crowd happens to have "find my" enabled on their phone, and you have "find my" enabled on your phone, after a while Apple will notice that the two of you are moving kind of in the same direction but not together. So they try and be helpful and alert you that you might be getting followed.
But f the alert came in email or from a browser, it's most likely a scam.
Here's a writeup when the warning feature was announced. You can read it and see if it matches the alert you got.
https://www.apple.com/newsroom/2024/05/apple-and-google-deliver-support-for-unwanted-tracking-alerts-in-ios-and-android/
Apple and Google deliver support for unwanted tracking alerts in iOS and Android
Apple and Google have worked together to create an industry specification Detecting Unwanted Location Trackers for Bluetooth tracking devices that makes it possible to alert users across both iOS and Android if such a device is unknowingly being used to track them. This will help mitigate the misuse of devices designed to help keep track of belongings. Today Apple is implementing this capability in iOS 17.5, and Google is now launching this capability on Android 6.0+ devices.
With this new capability, users will now get an [Item] Found Moving With You alert on their device if an unknown Bluetooth tracking device is seen moving with them over time, regardless of the platform the device is paired with.
If a user gets such an alert on their iOS device, it means that someone elses AirTag, Find My accessory, or other industry specification-compatible Bluetooth tracker is moving with them. Its possible the tracker is attached to an item the user is borrowing, but if not, iPhone can view the trackers identifier, have the tracker play a sound to help locate it, and access instructions to disable it. Bluetooth tag manufacturers including Chipolo, eufy, Jio, Motorola, and Pebblebee have committed that future tags will be compatible.
Sadly this feature, while useful, has mostly led to panic and confusion in the people getting the warning. And calls to the police to ask for help.