intellij-sdk-code-samples/topics/basics/architectural_overview/psi.md

The Program Structure Interface, commonly referred to as just PSI, is the layer in the IntelliJ Platform responsible for parsing files and creating the syntactic and semantic code model that powers so many of the platform's features.

• PSI Files
• File View Providers
• PSI Elements

See useful tools on how to inspect the PSI structure and its properties.