What do the "M" and "A" icons in the Project Navigator of Xcode 4 mean when I create a new project?

Those characters refer to the source control.

? - Unversioned
M - Modified
A - Added
A+ - Moved / renamed
U - Newer version of a file on source control
I - Item is being ignored (e.g. with the svn:ignore property).
! - Item is missing (e.g. you moved or deleted it without using svn). This also indicates that a directory is incomplete (a checkout or update was interrupted).

Ref: http://svnbook.red-bean.com/en/1.2/svn.ref.svn.c.status.html

Yes, it is related to source control.

"M" means the file has been modified since the last commit, and "A" means the file has been added since the last commit.

If you're using git, you can remove source control by deleting the .git directory in your project folder.

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This is taken from Sam's Book. I am having trouble finding information in Xcode Documentation.

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