Memory terminology in Mavericks Activity Monitory

For each process there is

• Real Memory (always at least as big as Memory)
  • Total Memory currently consumed by an application (including Virtual pages)
• Memory
  • Memory used in RAM
• Purgeable Memory
  • Memory which can be cleaned by MMU, if another process needs more real memory.

Then, for the system in total

• Physical Memory
  • The amount of RAM installed.
• Memory Used
  • The amount of RAM being used and not immediately available.
• Virtual Memory
  • The amount of disk or flash drive space being used as virtual memory.
• Swap Used
  • The space on your drive being used to swap unused files to and from RAM.
• App Memory
  • The amount of space being used by apps.
• Wired Memory
  • Memory that can’t be cached to disk, so it must stay in RAM. This memory can’t be borrowed by other apps.
• Compressed
  • The amount of memory in RAM that is compressed.
• File Cache
  • The space being used to temporarily store files that are not currently being used.