Unable to understand certain Cloud Storage cp command

[mountaincode2]

In the following page/section:

https://cloud.google.com/load-balancing/docs/https/ext-load-balancer-backend-buckets#copy-file

What does the following command signify:

gcloud storage cp gs://gcp-external-http-lb-with-bucket/three-cats.jpg gs://BUCKET_1_NAME/never-fetch/

1. What is `gs://gcp-external-http-lb-with-bucket/three-cats.jpg`. Where did `gcp-external-http-lb-with-bucket` come from. there was no reference to it in the tutorial.

2. Why does BUCKET_1_Name has the suffix `/never-fetch`?

I am looking at the following cp reference documentation as well, but unable to quite understand.
https://cloud.google.com/sdk/gcloud/reference/storage/cp