Event-driven architecture (EDA) is a software architecture paradigm that concerns the production and detection of events. In an event-driven architecture, events are used to trigger and communicate between decoupled services. An event can be defined as "a significant change in state".

An event-driven system typically consists of event emitters (or agents), event consumers (or sinks), and event channels. Emitters have the responsibility to detect, gather, and transfer events. Consumers, on the other hand, listen for events and react to them. The event channels are the means by which events are transmitted between emitters and consumers.

An event-driven architecture may be built on four logical layers, starting with the sensing of an event, proceeding to the creation of its technical representation in the form of an event structure, and ending with a non-empty set of reactions to that event.

Event-driven architectures have loose coupling within space, time, and synchronization, providing a scalable infrastructure for information exchange and distributed workflows. However, event architectures are tightly coupled, via event subscriptions and patterns, to the semantics of the underlying event schema and values.

Event-driven architectures are ideal for improving agility and moving quickly. They’re commonly found in modern applications that use microservices, or any application that has decoupled components. An event-driven architecture can help organizations achieve a flexible system that can adapt to changes and make decisions in real-time.

In summary, an event-driven architecture is a software architecture paradigm that uses events to trigger and communicate between decoupled services. It is commonly used in modern applications built with microservices and can help organizations achieve a flexible system that can adapt to changes and make decisions in real-time.