The chapter introduces the concept of Bose-Einstein condensation (BEC) in dilute gases, which was first observed experimentally in 1-95 for alkali metals. BEC occurs when particles in a gas reside in the same quantum state at very low temperatures, typically below 100 nK. The chapter highlights the unique properties of BEC, such as the ability to describe the condensate using mean-field theory and the large macroscopic quantum coherence that arises. The text covers the experimental techniques used to create and manipulate these systems, including laser cooling and magnetic traps. It explains how these methods enable the production of Bose-Einstein condensates, which have been studied in various atomic species like rubidium, sodium, lithium, and hydrogen. The chapter also discusses the theoretical framework for understanding BEC, including the Gross-Pitaevskii equation and the Thomas-Fermi approximation. Key aspects of BEC include the dynamics of the condensate, collective modes, and the behavior of vortices in rotating condensates. The chapter also explores the superfluid properties of BEC, such as the Landau criterion for dissipation and the two-fluid model. Additionally, it covers the effects of finite particle number and interactions on the condensate, as well as the properties of trapped Fermi gases and mixtures of bosons. The chapter aims to provide a comprehensive introduction to the field of BEC in dilute gases, covering both the experimental advancements and theoretical insights. It is designed to be accessible to readers with a general background in physics, making it suitable for both undergraduates and researchers.The chapter introduces the concept of Bose-Einstein condensation (BEC) in dilute gases, which was first observed experimentally in 1-95 for alkali metals. BEC occurs when particles in a gas reside in the same quantum state at very low temperatures, typically below 100 nK. The chapter highlights the unique properties of BEC, such as the ability to describe the condensate using mean-field theory and the large macroscopic quantum coherence that arises. The text covers the experimental techniques used to create and manipulate these systems, including laser cooling and magnetic traps. It explains how these methods enable the production of Bose-Einstein condensates, which have been studied in various atomic species like rubidium, sodium, lithium, and hydrogen. The chapter also discusses the theoretical framework for understanding BEC, including the Gross-Pitaevskii equation and the Thomas-Fermi approximation. Key aspects of BEC include the dynamics of the condensate, collective modes, and the behavior of vortices in rotating condensates. The chapter also explores the superfluid properties of BEC, such as the Landau criterion for dissipation and the two-fluid model. Additionally, it covers the effects of finite particle number and interactions on the condensate, as well as the properties of trapped Fermi gases and mixtures of bosons. The chapter aims to provide a comprehensive introduction to the field of BEC in dilute gases, covering both the experimental advancements and theoretical insights. It is designed to be accessible to readers with a general background in physics, making it suitable for both undergraduates and researchers.