A collection of components significantly showcased and mostly providing some way to view and preview those components and their related assets. As more React packages are developed with React to alleviate various aspects of development, the React community is also rising exponentially.

Some of the better known React Component Libraries are:

React Material-UI
React-Bootstrap
React toolbox
Ant Design React
PrimeReact
Office UI Fabric
Blueprint JS
React UI
Semantic UI React
React Spinner
Shards React
Argon Design System React

Why should one use a React Component Library?

There are many reasons that one has to make use of a React Component Library, some of which are:

Component Libraries have tens of components that are fully prepared for you and pretty much very unique.
Most of them also provide responsive interface options. Without the need for CSS or Grid libraries from third parties.
Increased delivery speeds plus the comfort for engineers.
Ability to successfully collaborate
Staying coherent and consistent
Versatility, flexibility & customization

How to choose the best React Component Library?

The library must be thorough. 90% of app scenarios should be addressed by components. That is where React-Bootstrap could lack at a few places.
Your UI design guides shouldn't be limited. The Material UI encourages you to use flat colors, the principle of flat design. However, it may not suit every other project.
It should have a strong follower/community size on GitHub.
Dynamic imports should be allowed.
They should be themed easily.

Apart from these, learn about your requirements and do a thorough analysis of the React Component Library you are about to choose. You can find more detailed articles on React Component Libraries over the internet that will better help you make the decision easily.