The "Employees" administration page lists all the user accounts that have access to your shop's back office.
By default you will find the account that was created during the store's installation, which is automatically set as SuperAdmin. The SuperAdmin has access to all of PrestaShop's features without restrictions.
You should make sure to create a new employee account for every actual employee that has anything to do with your online business. This means that you should never have a general user account that everyone can use, because you need to keep track of who did what on your shop.
Indeed, employees can edit orders, accept payments and refund customers, and you need to know who did what. Having a personal administration account for each employee is a good way for you to ensure that your team manages your shop responsibly.