What is the difference between buffer and cache memory in Linux?

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To me it’s not clear what’s the difference between the two Linux memory concepts : buffer and cache. I’ve read through this post and it seems to me that the difference between them is the expiration policy:

  1. buffer’s policy is first-in, first-out
  2. cache’s policy is Least Recently Used.

Am I right?

In particular, I’m looking at the two commands: free and vmstat

james@utopia:~$ vmstat -S M
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
5  0      0    173     67    912    0    0    19    59   75 1087 24  4 71  1
james@utopia:~$ free -m
             total       used       free     shared    buffers     cached
Mem:          2007       1834        172          0         67        914
-/+ buffers/cache:        853       1153
Swap:         2859          0       2859

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