Simple definition
Puppet enforces declared system configuration by comparing current and desired state and correcting differences.
Purpose and use
Puppet describes desired system-resource state to maintain consistent configuration across managed machines.
How does it work?
A server commonly compiles a node-specific catalog from declarations and available information; an agent compares and applies the relevant resources.
Example and verification
For repeated drift, compare the expected catalog, run reports and other tools changing the same settings.
Points to watch
Competing mechanisms can repeatedly restore conflicting values. Convergence also depends on providers, dependencies and module quality.
In short
Centralized declarations help maintain state when ownership of each configuration is clearly defined.