Topic name: "install_test2"
4 partitions (partition 0, partition 1, partition 2, partition 3) and your replication factor for this topic is 2. It means that data in your topic will be stored (replicated) in 2 brokers for redundancy. In Kafka every partition has a leader and all the requests from producers and consumers are sent to the leader.
Leader column (column B in your image) shows broker ids of the leader for each partition. (Kafka evenly distributes partition leadership between brokers for load balancing)
Replicas column (column C in your image) shows ids of brokers that replicates data for each partition. The first id represents preferred leader. It means Kafka will try to make this broker leader of partition.
ISR (column D in your image) means in-sync-replica. In Kafka when a message is sent to a topic-partition (firstly message is received and stored in leader) and if you have replication factor greater than 1, then replica broker(s) send fetch request and this data is replicated to other broker(s). A follower (replica) broker is in-sync if it is not far behind the leader (explained in below). If a partition leader fails, Kafka chooses an ISR as the new leader for failover.
From Kafka docs:
Configuration parameter replica.lag.time.max.ms now refers not just to
the time passed since last fetch request from replica, but also to
time since the replica last caught up. Replicas that are still
fetching messages from leaders but did not catch up to the latest
messages in replica.lag.time.max.ms will be considered out of sync.
