PDK (process design kit)
Beginner
The rulebook a chip factory gives designers. It says which shapes are allowed, how its switches behave, and which ready-made parts come with it.
Novice
The package a chip factory (foundry) gives designers for one manufacturing process: the rules for which shapes may be drawn, models of how its transistors behave, and usually a library of ready-made logic building blocks, described in files the design software can read.
Expert
Contains rule files for design-rule and layout-versus-schematic checks written for particular checking tools, SPICE transistor models, technology files, and cell libraries in LEF (shapes) and Liberty (timing and power) form. Commercial PDKs are covered by non-disclosure agreements, and some files are encrypted so only approved tools can read them. Open PDKs (SKY130, GF180MCU, IHP SG13G2) publish everything, currently as preview releases.