
Explanation

Box 1: Component library
Components are reusable building blocks for canvas apps so that app makers can create custom controls to use inside an app, or across apps using a component library. Components can use advanced features such as custom properties and enable complex capabilities.
By creating a component library, app makers easily share and update one or more components with other makers.
Component libraries are containers of component definitions that make it easy to:
Discover and search components.
Publish updates.
Notify app makers of available component updates.
Box 2: Component
A component can receive input values and emit data if you create one or more custom properties.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/component-library
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/create-component