Kernel
Takes care of memory management, CPU & Processes scheduling, drivers, the file system, networking, security and system calls.
Operating System (OS)
The kernel plus the user interaction (UI, I/O via Shell). An example is Linux (kernel) + GNU (user space tools).
BIOS (Basic I/O System)
Firmware that is loaded from ROM that initializes the OS start. It finds the bootloader and starts it, which then loads and starts the OS. Also used for basic configurations.
UEFI (Unified Extensible Firmware Interface)
A more advanced and modern approach to BIOS.
CP/M (Control Program/Monitor)
Early OS that was widely used in the 1970s to mid ‘80.
MS-DOS (MicroSoft Disk Operating System)
Rebrand 86-DOS and propiertary of Microsoft for 8086 processors, inspired by CP/M.
GNOME
GUI for Linux.
X11
Draws and manages the windows, used often as the base for GNOME. Low-level system.
Wayland
Same purpose as X11 with a more modern design and simpler architecture.
GNU
Core tools (shell commands, compilers, …) that together with the Linux kernel form a complete OS.