Akka is an open-source toolkit designed for building concurrent, distributed, and resilient applications on the JVM (Java Virtual Machine). It simplifies the development of complex systems by using the actor model, where individual components, called actors, communicate through message passing. This approach allows for better scalability and fault tolerance. Developed in Scala and also usable with Java, Akka provides features like location transparency, which means actors can interact without needing to know where they are located. It is widely used in industries that require high-performance applications, such as telecommunications and finance.