UNIX for Dummies Questions & Answers

 The first row, labeled Mem, displays physical memory utilization, including the amount of memory allocated to buffers and caches.
A buffer, also called buffer memory, is usually defined as a portion of memory that is set aside as a temporary holding place for 
data that is being sent to or received from an external device, such as a HDD, keyboard,
printer or network.  
   The second line of data, which begins with -/+ buffers/cache, shows the amount of physical memory currently devoted to system buffer 
cache. This is particularly meaningful with regard to application programs, as all data 
accessed from files on the system that are performed through the use of read() and write() 
system calls1 pass through this cache. This cache can greatly speed up access to data 
by reducing or eliminating the need to read from or write to the HDD or other disk.