When you declare a new property in the Properties block, you are providing a way for the shader to retrieve the tweaked value from the material's Inspector tab. This value is stored in the variable name portion of the property. In this case, _AmbientColor, _Color, and _MySliderValue are the variables in which we are storing the tweaked values.
In order for you to be able to use the value in the SubShader block, you need to create three new variables with the same names as the property's variable name. This automatically sets up a link between these two so that they know they have to work with the same data. Additionally, it declares the type of data that we want to store in our SubShader variables, which will come in handy ...
