Flink is an open-source stream processing framework designed for high-performance, scalable, and accurate real-time applications. It provides powerful abstractions for distributed stream and batch data processing, enabling developers to build complex data pipelines that can handle large volumes of data with low latency. Flink's advanced capabilities include event time processing, stateful computations, and exactly-once processing semantics, making it suitable for applications like real-time analytics, fraud detection, and machine learning.