Difference of Material, Shader

Now I am learning material and texture. My goal is for make object distort. for example, make a straight road to small hill. For creation of this effect. What do i need to use?
and fundamental question, what is difference of material and shader? what about postprocess?
I am still confused. On youtube, Unreal engine has a video " shader in UE4", it looks like material for me, but they call it shader. Can someone explain what difference of how we can use them separately?

A material is what you apply to geometry to give it a colour and pattern. A texture is a component of a material. Ashader is a small program that allows this material to be rendered at runtime.

Different industries use “shader” to refer to different, but related, things.
​​​​In game engines, such as Unreal, a “shader” is a piece of program that is going to take your material (together with mesh info) and send it to your graphics card to be “rendered”.