In this chapter, we discuss the main ideas behind Network Coding (NC). We initially introduce interflow network coding to build some background knowledge about the operations involved and the min-cut max-flow concept. However, the majority of this chapter is focused on intra-flow network coding with Random Linear Network Coding (RLNC). We mention its benefits in multihop and multipath communications, distributed storage, and security. The novelty of RLNC, namely recoding, will be explained, as well as the impact of the coding parameters on the coding performance and overhead. All our explanations will start with a high-level approach to introduce the reader to the overall concepts, followed by detailed explanations when needed to understand the following chapters in this book. Where detailed explanations for a particular topic are not directly needed for the context of this book, we provide the reader with references to the additional sources.