There is a very nice explanation of how an HTTPS connection is initiated at Moserware.
All too often, software developers work in an abstracted world and the details of what happens below the working abstraction layers is a complete mystery. Moser's explanation of the HTTPS connection initiation is a very clear and clean explanation of the process of establishing a trusted connection. It is well worth reading.
Editorial note: I'm hoping to find an opportunity in my schedule to resume writing more frequently.