The Built-in Render Pipeline is Unity's default render pipeline. It is a general-purpose render pipeline that has limited options for customization. The Universal Render Pipeline (URP) is a Scriptable Render Pipeline that is quick and easy to customize, and lets you create optimized graphics across a wide range of platforms. The High Definition Render Pipeline (HDRP) is a Scriptable Render Pipeline that lets you create cutting-edge, high-fidelity graphics on high-end platforms.