Erlang is a programming language designed for building fault-tolerant, concurrent, and scalable systems. It was developed by Ericsson for its telecom systems and has since been used in various fields such as web development, gaming, and financial services. Erlang's strength is in its ability to handle large numbers of concurrent processes while maintaining stability and responsiveness. It is often used in combination with other languages and frameworks to build complex systems that require high availability and fault tolerance.