Controlling data sharing, visibility, and access permissions within Microsoft Teams
Hello ! I'm Aymeric, and I'm here to help !
Your shared team calendar is available to anyone in the Teams group. When you add an event to it, everyone will see it by default.
However, your personal calendar, available on the left toolbar of Teams, is private and only visible to you - you decide if you want to share it. If you add an event to it, nobody will be able to see it - except you.
Feel free to ask if you have any other question !