Why does kafka-consumer-groups show the topics written to too in its describe

[Sachin Mittal]

Hi,
I am executing following command
bin/kafka-consumer-groups.sh --new-consumer --bootstrap-server
localhost:9092 --describe --group new-part-advice

It gives output like

GROUP                          TOPIC                  PARTITION
 CURRENT-OFFSET  LOG-END-OFFSET  LAG             OWNER
new-part-advice              advice-stream                 8
 114548551                  114548853              302
84-StreamThread-3-consumer_/10.9.56.84
new-part-advice              fname-stream                  1          584
                            610                      26
 84-StreamThread-4-consumer_/10.9.56.84
.........................

My pipeline is:
KStream<String, BeaconNode> input = builder.stream(Serdes.String(),
beaconSerde, "advice-stream");

input.
     ....
     foreach();


input.
     ....
     .through(Serdes.String(), valueSerde, "fname-stream");

So I don't understand why it is showing topic partitions from fname-stream
in describe, as the process is just writing to that topic and not consuming
from it.
Also what does lag in the case mean?

Thanks
Sachin