Concepts

architecture and subsystems

Architecture specific code: Architecture specific source code for the Linux Kernel.
device drivers: Linux device drivers can be found in the following source folders : /block (block devices), /drivers (most drivers: video, network,...), /sound (audio cards)
file systems: This includes all the file systems supported by the Linux Kernel, and the VFS (virtual file system) which provides a common interface abstraction for all the file systems.
Kernel code and process management: Manages processes, threads, scheduling, stacks, signalling, time...
memory management: Memory management for physical and virtual memory
network stack: Networking code (IPv4 and IPv6 networking stacks, BSD socket, routing, filtering, etc)
system call interface: The system call interface is the set of functions exposed by the kernel to the user space.

linux components

Linux kernel modules: Loadable Kernel modules can be loaded and unloaded into the kernel on demand. Most device drivers can be used as kernel modules.
vmlinux: Linux kernel in a statically linked executable file format.

apparmor: The apparmor Linux Security Module controls the access rights of applications (file access, network access, etc), based on MAC security (Mandatory Access Control, administrator policy)
loadpin: The loadpin Linux Security Module ensures that all kernel modules are loaded from the same filesystem
linux security module (LSM) framework: The LSM framework allows the Linux kernel to support a variety of computer security models, by using security extensions.
Security Enhanced Linux (selinux): The selinux Security Module provides access control security policies based on MAC (mandatory access control)
Simplified Mandatory Access Control Kernel (Smack): Smack is a kernel based implementation of mandatory access control that includes simplicity in its primary design goals.
tomoyo: TOMOYO is a Mandatory Access Control (MAC) implementation for Linux.
yama

Extended Verification Module (EVM): EVM protects a file's security extended attributes against integrity attacks.
Integrity Measurement Architecture (IMA): IMA maintains hash values for sensitive files. If used, the TPM (Trusted Platform Module) stores an aggregate integrity value over this set.
Linux integrity subsystem: Detects files that have been altered
Linux key retention service: This services caches authentication tokens and access keys in the kernel for the use by kernel services.

Linux Application Binary Interface (ABI): Linux ABI defines how data structures or routines are accessed in machine code: it is an architecture/hardware dependent format.
Berkeley Packet Filter (BPF): BPF allows a user-space program to attach a filter onto any socket and allow or disallow certain types of data to come through the socket. For example, a tcpdump process may want to receive only packets that initiate a TCP connection.
Executable and Linking Format (ELF): Common standard file format for executable files, object code, shared libraries, and core dumps.