diff --git a/MdePkg/Include/Uefi/UefiBaseType.h b/MdePkg/Include/Uefi/UefiBaseType.h
index 431e70ba19..d14215619f 100644
--- a/MdePkg/Include/Uefi/UefiBaseType.h
+++ b/MdePkg/Include/Uefi/UefiBaseType.h
@@ -45,7 +45,15 @@ typedef UINTN                     EFI_TPL;
 /// Logical block address.
 ///
 typedef UINT64                    EFI_LBA;
+
+///
+/// 64-bit physical memory address.
+///
 typedef UINT64                    EFI_PHYSICAL_ADDRESS;
+
+///
+/// 64-bit virtual memory address.
+///
 typedef UINT64                    EFI_VIRTUAL_ADDRESS;
 
 ///