What is version control?

Version control is the practice of tracking and managing changes to software code. Version control systems are software tools that help software teams manage changes to source code over time. They are especially useful for developer teams, since they help them to reduce development time and increase successful deployments. Version control software keeps track of every modification to the code in a special kind of database. If a mistake is made, developers can turn back the clock and compare earlier versions of the code to help fix the mistake while minimizing disruption to all team members.

Why should I use it?

You should use it, because it help you and it keeps track of your changes.
Here is some benefits

What is Git? and why use it?

Git is Version Control System and GitHub is a hosting service for files and projects that use Git. Apart from that, Version Control System is pretty self-explanatory term. It helps track the different versions created over time and provide an space efficient technique to record history and changes made to files and directories.