Glossary
sudo
Running a single command with administrator privileges.
sudo lets a permitted user run one command as root (or another user), after authenticating with their own password. It checks a policy file (/etc/sudoers, edited only via visudo) and logs every invocation with user, terminal and command.
It also sanitizes the environment before executing, which is why aliases vanish and PATH differs under sudo. And because redirection is performed by your shell, writing root-owned files needs the write inside the privileged process: echo x | sudo tee /etc/file.
See it in practice
$ echo "127.0.0.1 dev.local" | sudo tee -a /etc/hostsThe write happens inside the privileged process. sudo echo > file would fail, because your shell does the redirecting.
Where you'll meet it
Temporary privilege, audited — and why sudo won everywhere.
teeSplit a stream: watch output live while saving a copy — and write files with sudo.
RootThe administrator account with unrestricted privileges.