Celery is an asynchronous task queue that allows running time-consuming Python functions in the background. It improves user experience by minimizing request/response cycles and offloading intensive processes. Celery provides scalability, flexibility, and customization options. Common uses include sending emails asynchronously, running computational jobs, and interacting with external APIs. A Celery architecture includes a producer that puts tasks in a broker queue, workers that consume tasks, and a results backend that stores task outputs.