What should I think of the "buffers" and "cached" memory? should I think they are part of free memory?

This is a verbatim copy of what I wrote down when I had this same question:

             total       used       free     shared    buffers     cac
+hed
Mem:       1034332     983572      50760          0     149028     530
+132
-/+ buffers/cache:     304412     729920
Swap:       131064       9856     121208

Mem:             A          B          C          D          E        
+  F
-/+ buffers/cache:          G          H

G+H = A
E+F+G = B   ## probably D+E+F+G
C+E+F = H   ## probably C+D+E+F
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