Points to a
page table, and also contains
bit flags about the relevant region of
memory.
On the Intel x86 architecture starting from 386, the PDE is a 32-bit entry in the PDT that contains a pointer to the page table describing a region of 4MB in the process address space. The offset of these 4MB in the address space is determined acccording to the offset of the PDE inside the PDT. Bits 0-11 of a PDE contain the same bit flags that a Page Table Entry contains. The rest of the bits, 12-31, define the physical address of the page table for that PDE, which needs to be valid or not according to the bit flags.