Currently by default you would have an administrator account. You can create any no. of user accounts in your system(laptop/computer). While creating a new user account, you are given an option to create an administrator or standard user account.
When you are logged in through administrator account, you have privileges as you can make changes to the system configuration, install new applications etc. With standard user account still work in the system, you can do all sorts of copy, paste, creating new files, virtually everything, except for changing any system configuration related things, you can not install most of the applications as they require you to change the system configuration.
Also, only an administrator can create/delete new user accounts.
Hence, it is advisable that the owner of the system should have the admin account with password and others using the system should log into standard user account.
After creating the new account, your old account still remains unless you delete it manually. Your new account will have new desktop settings(so, you might have create some new shortcuts for existing applications), different documents and settings etc. you still can look into your old user account folders.