Physical: Indicates the number of bytes of physical memory available.

Swap: Indicates the number of bytes available in the paging file.

Virtual: Indicates the number of bytes of unreserved and uncommitted memory in the user mode portion of the virtual address space of the calling process.

Free: Specifies a number between 0 and 100 that gives a general idea of current memory utilization, in which 100 indicates no memory use and 0 indicates full memory use.