After you have installed or upgraded your Windows, you will get a Welcome Screen with the time and date. Just click anywhere to go to the User Accounts Screen.
This screen lets you choose which user you want to log in to from the lower-left corner. After choosing the right user, and entering a password if necessary, you will see the Windows Desktop.
The Windows Desktop is simply your operating system main screen. Here you have access to an array of tools like the Start Menu, Taskbar, and other icons. Windows 10 also introduces a search box in the Taskbar, which facilitates browsing both your computer and the Web.