A Task State Segment (TSS) is a binary data structure specific to the IA-32 and x86-64 architectures. It holds information about a task. In Protected Mode the TSS is primarily suited for Hardware Task Switching, where each individual Task has its own TSS. For use in software multitasking, one or two are also generally used, as they allow for entering Ring 0 code after an interrupt. In Long Mode, the TSS has a separate structure and is used to change the Stack Pointer after an interrupt or per...| wiki.osdev.org
Interrupts are signals from a device, such as a keyboard or a hard drive, to the CPU, telling it to immediately stop whatever it is currently doing and do something else. For example, a keyboard controller can send an interrupt when a character key was pressed. Then the OS can display the character on screen immediately, even if the CPU was doing something completely unrelated before, and return to what it was doing afterwards. When a specific interrupt arises, the CPU looks up an entry for t...| wiki.osdev.org
The Global Descriptor Table (GDT) is a binary data structure specific to the IA-32 and x86-64 architectures. It contains entries telling the CPU about memory segments. A similar Interrupt Descriptor Table exists containing task and interrupt descriptors.| wiki.osdev.org