One of the things that every Apple user should know is the ins and outs of their Apple ID account and therefore the devices through which it has been accessed at some point. By this we mean that Apple keeps a record of all the devices that at some point have been connected to the Apple ID and therefore they have had access to all the data that is stored in iCloud.
When a device connects to iCloud Apple send an email to the associated Apple ID informing that a connection has been made from a certain device.
Now, it may be that at a certain time and on days like today when there are many discounts on Apple products, you decide to put your Mac or iPhone on sale to acquire a more modern one. We want you to know that until you delete the device from your account yourself, it will continue to exist in the same as a connection to your iCloud cloud has been made from it, so over time it can give you a scare and believe that they have connected without your permission when it was surely you who did it at the time.
In order to see the devices that are registered as they have been used to connect to your iCloud cloud at some point you must enter the following Apple website and enter your Apple ID to be able to manage them and in any case delete them once and for all if they are no longer of your property.
