What is a scm and blk files?

I'm frustrated trying to determine what are scm and blk files? I have theses files from a download and need to open them,  for this tutorial.

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instead of unzipping an App Inventor project (aia file), you should upload that file directly to App Inventor. The unzipped files (scm or blk) will not help.

In case you unzipped an old App Inventor Classic project (zip file), you can convert it into an aia file here http://appinventor.mit.edu/explore/classic.html

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