Epidemic algorithms have emerged as a simple, yet effective solution for disseminating live streaming contents to a large audience. Typically, the use of epidemic algorithms is motivated by the fact that they do not rely on a specific underlying structure to work, so they are very robust against network dynamics and volatility. However, the performance of these algorithms is still little understood. This chapter is intended as an introduction to epidemic live streaming. We propose some simple metrics to understand the behavior of a diffusion algorithm, and we use elementary diffusion schemes to understand the basics of the diffusion process, for both homogeneous and heterogeneous systems. The approach that we propose mixes theoretical results, when available, with empirical observations in order to give the best possible insights.