The Linux operating system (along with most Unix and Unix-like systems) has user accounts set by default to a restricted user, meaning system-level changes cannot be made without elevating permissions. For this purpose, the sudo command can be used, which temporarily provides elevated root-level permissions to run a single command. This functionality is similar to the more recently implemented User Account Control on Windows.
Normally, when you try to elevate using sudo, you have to type in your password. This can be annoying when you need to perform a series of commands, typing in your password for each one.
If you're the only user on your computer, you can enable sudo to operate without a password.
This is accomplished simply by adding the line:
user ALL=(ALL) NOPASSWD: ALL
to the /etc/sudoers file.
Note that it's still not recommended to leave your system like this, as any piece of software run on your machine can potentially use this to gain root permission and do something malicious. Unless you properly vet all software you run on your machine, you should disable this setting as soon as is reasonably practical. Since I can pretty much guarantee that all software you run is not properly vetted, it isn't safe to leave this setting permanently.