A private folder

A private folder is a special folder available for each Salesforce user, and is also known as the My Personal Custom Reports folder for a report folder. For dashboards, it is called My Personal Dashboards (in Classic), or Private Dashboards (in Lightning Experience). In Lightning Experience, reports stored in this folder are called Private Reports.

All reports and dashboards in this folder are only visible to yourself; no one is supposed to be able to access, change, or delete the reports and dashboards in this folder. But if your admin has the same login access as you, she or he will be able to login and act as you with your reports and dashboards in the personal folder, here is the screenshot when you create a new dashboard:

As you can see in the previous screenshot, this user has a choice to store the new dashboard into the Private Dashboards folder, or a public folder called Shared Dashboard Folder.