Learn the basics about object oriented programming (OOP) in c#.
I’m using monodevelop (and unity) here to explain, but you can (and probably should) use Visual Studio for example.
I use these principles in pretty much all my unity-coding tutorials; so if you are completely blank in this concept, you probably should follow it.
If you are more experienced I would like to hear your opinion too!
Hopefully you will be a little bit more understanding about these principles after you have seen this video.