When you install ubuntu(or ubuntu based distros) you are locked out of the root[admin] account - it exists but you're not given the password.
The account you made is a desktop user account with access to sudo, and you need to use sudo to perform tasks that require administrative privileges.
(for some info on group permissions)
(info about sudo and the root account)
If you don't want access to sudo for whatever reason (eg. a shared or public user account, or multiple users on the computer), you can make a new user that doesn't have permission to use sudo, and switch to the one you made on install when you need to install new programs and such. This way you can log into the new account for everyday use and let other people use it without needing to worry about them messing about in your system.
(for making new users and such)
By default, a user added in this way won't be given sudo privilege unless added to the admin group.