This document discusses various types of horizontal agreements under EU competition law. It summarizes that horizontal agreements between competitors can involve price fixing, market sharing, limiting output, or collusive tendering. It notes the key tests used to analyze these agreements, including effects on competition and market power. The document also reviews exceptions for agreements that may generate efficiencies, such as certain joint ventures, research and development collaborations, and specialization agreements, provided they do not contain hardcore restrictions like price fixing.