Can someone explain to me the Unity3D API ?!

I’m A Beginner, I learned javascript online, now I want to learn the API of the Unity3D Game Engine…I Don’t know if it’s called API or I’m wrong, but for exapmle…

I Want to make a car move in unity, so codes on the internet are having things like “input.GetAxis”, “motorTorque”… what are these!? Not just these but anything like them…what they do ? Any Explanation ?! Books ?! PDFs?! HELP ME PLEASE

Answers is primarily for specific technical questions. Browse the learn section first. There are hundreds of good tutorials here.