Consumers read from the topic (the underlying partitions) and maintain the offset last read themselves, allowing for easy replay, strict ordering within a single partition, and completely disconnected pacing from producers. The optional "key" for each message allows for compaction so only the latest key/value pair is kept in a topic.

It's definitely not a database but works well for replicating them, as well as doing most of the work of a typical message queue / service bus system.