HarryC - yes it is an interesting topic and obviously there are entire books and courses devoted only to this type of construction.
ChicagoChicago - Prestressed does not differ significantly from post-tensioned in concept, just in practice. With prestressed, the cables are stressed first then concrete is placed around the cable(s) rather than casting then stressing. Once the concrete is sufficiently cured, say 1 to 3 days, the cables are cut (the cables will be stressed and anchored to big steel anchor heads at each end of the casting and the cables then pass through the concrete formwork). By cutting each strand, the tension is now applied along the line of action for the strand - in effect putting the concrete into compression along that same line. The cables bond directly to the concrete - they are not encased in a sheath and do not need to be grouted. Prestressed concrete design does not involve losses like friction or wobble; but both prestressed and post-tensioned will have some "long-term" losses such as relaxation, shrinkage, and creep.
Prestressed is generally suited to being done on assembly lines under controlled conditions whereas post-tensioning is perhaps better suited to "field" construction for large flat-work (slabs).
Here is a good view of a "clam shell" style steel form used for prestressed concrete girders. It is essentially two halves that are opened (to allow placement of steel and arranegment of strands) or closed when concrete placement is underway. There is even a walking platform to allow workers to place concrete easily at the top. What you don't see in this picture are the two steel bulkheads that would contain the ends of the pour and through which the steel strands pass through on their way to the anchor blocks.
