The PrestaShop back office is the name used to describe the administration panel of your PrestaShop store in this user guide. You will spend most of your time in this panel, as everything that the user sees is handled directly through the back office: adding/editing/removing products, handling carriers, building packs, creating vouchers, keeping contact with customers, improving your shop, etc.
During the install process, the /admin folder is renamed into something unique to your shop (for instance, /admin091anufki), for security reasons. Use that new folder name to access your shop (for example: http://www.example.com/admin091anufki).
The name change is done automatically by PrestaShop. Be careful to memorize that folder name the first time you access it after the installation!
You will see the login page for your shop's control panel.
Enter the e-mail address and password that you registered with when installing PrestaShop. Click in the "Log In" button, and you are taken to the back office's dashboard, a sort of welcome page for this control panel.
From this step onward, you can begin to configure your shop and sell products to your customers.