The specification currently assumes a certain level of knowledge about MQTT. We should elaborate page 1 "Abstract" and "Features of the protocol" to communicate core information:

e.g.,
1. MQTT is a client server protocol.
2. Communication is underpinned by TCP/IP

A definition should be offered for terms such as:

1. client
2. server
3. connection
4. Publisher
5. Subscriber

What is the relationship between TCP Connections, Clients and "MQTT Sessions".