Unity Materials

Material

Material is a combination of properties, texture and shader.

Properties

The basic properties of the object like red color for example.

Texture

The texture that you want to give the object, for example a repeatable texture of bricks wall (if you are looking for textures in google add the tillable, seamless, repeatable word)

Shader

Define which texture or properties the material can contains, for example in the diffuse shader the light is diffuse equally on the surface. 
Another shader for example is the specular shader, with this shader the object gets a shiny effect.