What is sb protocol and how is works internally?

I have configured a notification hub using Azure portal for implementation of push notifications for mobile apps. On navigating to the Access Policies section, I see couple of policies with names: DefaultListenSharedAccessSignature and DefaultFullSharedAccessSignature as shown in the below diagram. Both the policy names contain connection string. One of the connection string is as follows:

Endpoint=sb://expedia.servicebus.windows.net/;SharedAccessKeyName=DefaultFullSharedAccessSignature;SharedAccessKey=JnVgQvxxxxxxxxxxxxxxxxxxxxxxxy1HgWUfUo=

I want to understand what is sb protocol here and want to how it works internally and does it depends on HTTPS.

I have to access the above endpoint from a remote server. How to consider the above while white listing the proxy rules to allow access to the above endpoint.

sb is just an endpoint schema that we understand, and it's not an actual protocol. The actual protocol is https.