Simple definition
The setuid permission bit can make a program run with the file owner's effective user identity.
Purpose and use
The setuid bit on an executable can cause it to run with its owner’s effective identity.
How does it work?
The kernel applies this transition according to file, mount and security rules; real and effective identities may differ.
Example and verification
For a privileged executable, review ownership, permissions and whether the elevation is necessary.
Points to watch
setuid is neither encryption nor general access to data. Restrictions such as nosuid can prevent its effect.
In short
Elevation changes process context and requires software designed to handle those privileges safely.