What exactly is different about a lens in Macro mode? Does the lens alter
its optics in some way to focus more closely?

My Galaxy S7 lens doesn't seem to have enough space inside to shift any
elements in a different way. Although my point and shoot has a lens which
comes forward and is made of 6 elements in 5 groups. How do these cameras
provide Macro mode?

If a camera can provide close up macro focusing then why isn't it provided
as part of Normal mode?