why can I login MacBook with different usernames of the same user I have only one user on my MacBookPro.
When I check the Users &amp; Groups panel, I can see the username of this only user is "xxxyyy", then I also check the home directory of this only user in Terminal and it shows "/Users/xxx".
As a result, I can login my MacBook with the name "xxxyyy" or the name "xxx" as well.
It puzzles me a lot, Could anybody please give an explanation to this ~
When I entered my user name, it has, as standard, the long name and a short name based on the long name - that you can edit to be different if you want.

You can check in the system preferences : users and groups...