Grouping related systems together. Topics are central concepts in Kafka that decouples producers and consumers. 

Producers pushes messsages into Kafka .

Consumer take message from Kafka

https://www.baeldung.com/spring-kafka

A topic is category or feed in which records are published or saved> Topics are used to organize all kafka records

Messages get written and read from topics. A topic can be thought of as analogous to a directory or folder in an operating system.