2nd uv channel, lightmap, color grid, uv grid help Blender help needed

So I’m making strides in Blender. I figured out that the UV map orientation determines the attribution of texture orientations. Now I have to figure out the more complicated settings;

  1. what is the two uv channels, what do I use it for? When I do the unwrap in Blender it unwraps everything onto the uv/image editor but it’s tough to tell exactly how the uv unwrap is interacting with the images or the uv channels. The UV unwrap gets highlighted on the second UVmap and if I select the first one (as in the second uploaded image) it becomes not highlighted but the panels remain visible. Is one supposed to be base UV’s and the other lightmass UVs? What’s the difference? How do I set them up in the material editor?

  2. what are lightmaps for, do I need to create a lightmap image for more complex meshes? Do lightmap images need to be associated with uv channels somehow?

  3. do I need to add color grid or uv grid images in Blender?

  4. If I scale the UV smaller so I can rotate disoriented UV panels to other parts of the UV/Image editor will it mess with the texture coordinates?

  5. how should I correlate texture coordinates on the texture sample in the material editor? Does the texture coordinate index in the material correlate to the uvmap? What do I set the coordinate index to?

Appreciate any help