This document provides an overview of swarm intelligence and various swarm intelligence algorithms. It defines swarm intelligence as the collective behavior of decentralized, self-organized systems, both natural and artificial. Examples of swarm intelligence in nature include ant colonies, bird flocking, fish schooling, and bacterial growth. Several swarm intelligence algorithms are described, including particle swarm optimization, ant colony optimization, artificial bee colony, bacterial foraging optimization, and gravitational search algorithm. These algorithms were inspired by behaviors observed in swarms in nature.