What does free command witj -o indicate , man page says it disables buffer adjusted line. It subtracts buffer memory from free memory. What does this mean
Buffers and cache use up memory. The used/free values include display memory being used when it is consumed by buffers and cache. See this page for a description. http://www.linuxatemyram.com/
Here is the difference on my system. Basically my system has 2,282,608 kbytes of memory that could be used by programs if it was needed. But a significant portion of that is currently being used for buffers/cache which speed up the normal operation of the system. If a program requested RAM the memory allocated to the cache would be released and allocated to the program.
In addition to what @Zoredache said the calcs are like:
how much memory is really being used:
how much memory is really free:
With the above calculation, it makes more sense now