(some aspects of this topic require an in-app purchase; see note below)
Render Passes perform the actual rendering of all the Render Pipeline States in your project. They draw each Render Pipeline State's assets (models, textures, etc.) using that Pipeline State's shaders, and combine them into a single scene render.
Each Render Pass has its own camera that can be moved independently:
If a render pass is rendering to more than one color attachment, you can select which one will be shown on the component itself using its drop-down menu. Regardless of which one you choose there will always be an output texture for each color attachment, so you can always see all of their output on the Shader Path window.
Note that each Render Pipeline State that is connected to a Render Pass must render to the same color attachments.
Each render pass has a default output resolution that you can change by doing one of the following:
From here you can edit the resolution of the render pass. Doing so will update the resolutions of this render pass' depth attachment texture and all of its color attachment textures.
The free version of ShaderScope allows for a single Render Pass to be used in each project. If you'd like to add more than one, the ShaderScope Multiple Render Passes in-app purchase allows you to do that.
There is a special type of Render Pass can be created to be associated with a light in your scene and render its shadow map. Those are distinct and don't function in quite the same way as the more general version described here. See Shadow Maps for more details.