sharedmaterial and sharedmesh

this is from a youtube tutorial and im converting skinnedMeshRenderer to a regular mesh.
what is sharedmaterial and what is sharedmesh?
i cant really understand the manual.can someone use simple english to explain?my english is bad

Code (CSharp):

1. void convert()
2.     {
3.         SkinnedMeshRenderer skinnedMeshRenderer = GetComponent<SkinnedMeshRenderer>();//Unity uses the Skinned Mesh Renderer component to render Bone animations, where the shape of the Mesh is deformed by predefined animation sequences.
4.         MeshRenderer meshRenderer = gameObject.AddComponent<MeshRenderer>();//The Mesh Renderer takes the geometry from the Mesh Filter and renders it at the position defined by the object’s Transform component.
5.         MeshFilter meshFilter = gameObject.AddComponent<MeshFilter>();//The Mesh Filter takes a mesh from your assets and passes it to the Mesh Renderer for rendering on the screen.
6.  
7.         meshFilter.sharedMesh = skinnedMeshRenderer.sharedMesh;
8.         meshRenderer.sharedMaterials = skinnedMeshRenderer.sharedMaterials;
9.  
10.         DestroyImmediate(skinnedMeshRenderer);
11.         DestroyImmediate(this);
12.     }
13. }