Zookeeper is an open-source software that helps manage distributed systems. It provides a centralized service for maintaining configuration information, naming, and providing distributed synchronization. This makes it easier for applications to coordinate and communicate with each other in a reliable way. Zookeeper is often used in conjunction with other big data tools like Apache Hadoop and Apache Kafka. It ensures that these systems can work together smoothly by keeping track of their states and configurations. This helps prevent issues that can arise in complex, distributed environments, making it a crucial component for many modern applications.