On this page,  INFOPLUS displays how your RAM is being used.

Total conventional memory: This is the type of memory typically used by DOS
                           and programs.
Free conventional memory:  This is the amount of memory left after DOS,
                           drivers, and TSRs take some.
Extended memory: This is the amount of memory on a 286/386/486 that is
                 above the 1 Meg mark. This may not be the total amount.
                 Some programs that use extended memory subtract what they
                 use, and report that to INFOPLUS. Also, programs such as
                 QEMM and HIMEM.SYS will 'steal' all of it because they
                 want to manage it in a way that allows different programs
                 to share it.
XMS driver: One of the major problems with extended memory is that there
            was no correct way of accessing it. There was a major problem
            programs interfering with each other. XMS stands for eXtended
            Memory Specification. It's a standard interface for programs to
            access extended memory.
            HMA stands for High Memory Area. On a 286/386/486, it's
            possible to access the first 64K of extended memory without
            going into a special CPU mode. Access to that area is done by
            enabling or disabling A20 (address line 20.) DOS 5 is capable
            of placing some of it's code and BUFFERS in the HMA. Infoplus
            tell you if it is using it, and how much is left over.
            The XMS driver also handles Upper Memory Blocks (UMBs).
            Infoplus will display if any area is available, and how big the
            largest block is.
DPMI driver: With the growing complexity of programs, some need more than
             the normal 640K of memory to run. DPMI stands for DOS
             Protected Mode Interface. It allows programs to run in
             protected mode, yet still access regular DOS functions. It was
             introduced with Windows 3, and offers greater protection from
             interference by other programs than VCPI. DPMI is available on
             286/386/486 computers.
Expanded memory: Expanded memory was one of the first ways of getting more
                 than 640K in a computer. It does this by taking the extra
                 memory and breaking it up into 16K 'pages.' It puts up to
                 4 of these at a time in a 64K window in an unused area of
                 memory accessible to the CPU (called the page frame.)
                 Expanded memory is often called EMS (Expanded Memory
                 Specification.)
                 All EMS drivers have an internal driver name of EMMXXXX0.
                 The latest specification is 4.0. Unfortunately, 4.0
                 requires some hardware specifics for FULL compliance. Many
                 4.0 drivers are not hardware compliant. Their hardware is
                 in compliance with the older standard, numbered 3.2.

                 Some EMS drivers also support VCPI (Virtual Control
                 Program Interface.) This was the first standard to allow
                 programs to run in protected mode, yet still access DOS
                 functions. Unfortunately, it's too easy for programs to
                 interfere with each other, or unncessarily block another
                 VCPI program from working. VCPI is only available on
                 386/486 computers.