Incorporating distributed energy resources in current energy systems is essential for improving energy management, reducing consumption and waste, increasing renewable participation, and mitigating environmental impact. Within this framework, integrated energy systems (IESs) are designed to holistically manage entire energy systems by leveraging potential resources across multiple vectors and sectors, including electricity, gas, heat, cooling, fuels, energy storage, hydrogen, and transport, while considering technical, economic, or environmental criteria. This chapter provides a review of the infrastructure, operation methodologies, and market approaches of IESs, utilizing a multi-layer architectural model. A significant focus of this review lies in the role of communities, serving as the foundation for two introduced concepts: BCoMuns (buildings, communities, and municipalities), representing elemental components of the lower layer, and integrated prosumers (IPs), key constituents of the upper layer. This innovative perspective enriches the understanding of IES, highlighting the interconnectedness of community-centric energy systems within the broader energy landscape.