Global descriptor table

The Global Descriptor Table is a table used by Intel's Protected Mode to manage memory, multitasking, and various gates. It has a maximum of 8192 descriptors of eight bytes each. Segments can be entered in the GDT which, for example, address and protect the main memory in a certain area.

To access a segment, you have to load a selector into the segment register (CS, DS, ...) and you can then access it.