key.deserializer: It is a Deserializer class for the key, which is used to implement the 'org.apache.kafka.common.serialization.Deserializer' interface.

value.deserializer: A Deserializer class for value which implements the 'org.apache.kafka.common.serialization.Desrializer' interface.

bootstrap.servers: It is a list of host/port pairs which is used to establish an initial connection with the Kafka cluster. It does not contain a full set of servers that a client requires. Only the servers which are required for bootstrapping are required.

group.id: It is a unique string which identifies the consumer of a consumer group. This property is needed when a consumer uses either Kafka based offset management strategy or group management functionality via subscribing to a topic.

auto.offset.reset: This property is required when no initial offset is present or if the current offset does not exist anymore on the server. There are the following values used to reset the offset values:

earliest: This offset variable automatically reset the value to its earliest offset.

latest: This offset variable reset the offset value to its latest offset.

https://www.javatpoint.com/creating-kafka-consumer-in-java