Per-pixel and per-vertex lights

If you use the default Forward rendering path, each realtime Light component can be one of the following types:

• A per-pixel light, which lights each pixelThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info
  See in Glossary of an object accurately.
• A per-vertex light, which lights each vertex of an object accurately. Unity interpolates lighting for the pixels between vertices.

Per-pixel lights give more accurate results but reduce performance.

The Built-In Render PipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
See in Glossary also sets some lights as Spherical Harmonic (SH) per-vertex lights, which are the least accurate but render the fastest.

For more information, refer to the following:

• Light limits in the Universal Render Pipeline (URP)
• Per-pixel and per-vertex lights in the Built-In Render Pipeline

Additional resources

• Choose a lighting setup
• Introduction to rendering paths