A Front End library is a file or a piece of pre-written code that is helpful to the user by reducing the time consumed.
These code libraries help their users to minimize their time in writing long lines of code, and increase their productivity. For example- Front end libraries like [Bootstrap](https://getbootstrap.com/) provide a framework for users to build upon and reduces the time consumed, while allowing flexibility to the user.
Since these are front-end libraries, they work with HTML, CSS and JavaScript and modify the layout, style and behavious of the page in a browser respectively.
#### More Information:
1. [Some Good Front End Libraries](https://medium.com/learnwithrahul/introduction-to-some-kick-ass-front-end-libraries-tools-963f55152f4b)