Kafka is a high-throughput, persistent, and publish-subscribe messaging system. It uses a producer-broker-consumer model where producers publish messages to topics, brokers distribute messages to consumers, and consumers subscribe to topics. The document discusses how game company Wooga uses Kafka for event streaming to track metrics like requests per second and installs per minute. It also describes Wooga's open source Kafka libraries for Ruby and Erlang called Kafkaesque.