"Zookeeper keeps track of status of the Kafka cluster nodes and it also keeps track of Kafka topics, partitions etc. Zookeeper it self is allowing multiple clients to perform simultaneous reads and writes and acts as a shared configuration service within the system."
zookeeper is central point of Kafka without it cluster will not work properly. Zookeeper store metadata.
In future kafka versions (kafka roadmap on confluent) architecture will be simplified and zookeeper can be removed (rather step by step).
