Explanation/Reference:
Explanation:
Within a namespace, you can use one or more instances of three different communication mechanisms, each of which connects applications in a different way. The choices are:
Queues, which allow one-directional communication. Each queue acts as an intermediary (sometimes

called a broker) that stores sent messages until they are received. Each message is received by a single recipient.
Topics, which provide one-directional communication using subscriptions. A single topic can have

multiple subscriptions. Like a queue, a topic acts as a broker, but each subscription can optionally use a filter to receive only messages that match specific criteria.
Relays, which provide bi-directional communication. Unlike queues and topics, a relay doesn't store in-

flight messages; it's not a broker. Instead, it just passes them on to the destination application.
References: https://docs.microsoft.com/en-us/azure/service-bus-messaging/service-bus-fundamentals- hybrid-solutions