OpenLayers is an open-source, high-performance JavaScript library for displaying map data in web browsers. It provides an extensive set of capabilities for adding interactive maps to web applications. OpenLayers supports a variety of map sources, including commercial data providers and various types of free map data. It allows users to easily implement complex geographic information like tiled, vector, and 3D maps. Ideal for building applications that require detailed spatial functionality and customization, OpenLayers integrates smoothly with other web technologies and frameworks.