The EU network codes and guidelines are a detailed set of rules pushing for the harmonisation of national electricity markets and regulations. The areas for the development of network codes and guidelines were set out in the Third Energy Package. By the end of 2017, a total of eight network codes and guidelines entered into force: three grid connection codes (RfG NC, DC NC and HVDC NC), three market codes (FCA GL, CACM GL and EB GL), and two operation codes (SO GL and ER NC). The major part of this text covers the market codes. The reader is guided through the sequence of electricity markets in place in the EU: forward markets, the day-ahead market, the intraday market and finally the balancing markets. The establishment of these different markets in a national context and their integration is discussed. Links with the operation codes are made where relevant as electricity markets cannot be decoupled from system operation. Additionally, two connection codes (RfG NC and DC NC) are covered; the scope of these codes is described and technical requirements are clarified. In the last chapter, network, market and consumer data is addressed. More specifically, the level of harmonisation in data exchange processes and access to these different types of data is discussed. In each section, basic concepts are explained, we highlight what is set out by the codes, and we also refer to some of the relevant academic literature. Finally, the report also points out where provisions in the Recast of the Electricity Regulation, which is part of the Clean Energy Package, impact the existing network codes and guidelines.