Ok Chris, by CAM Job I mean one operation in the Job Tree, that being where all you CAM Jobs for that particular part are located - like the Feature Tree in SolidWorks.

When you create a new CAM part, SolidCAM creates a clone of the part (which I call the "seedpart") you want to program and calls it the "DesignPart", storing it in a SolidWorks Assembly along with another part SolidCAM creates called,logically enough, the "CAM part". I call this assembly "the main Assembly". This CAM part is the place to create sketches, surfaces etc that you need when programming; you can create sketches in the top level of the assembly but if you have big complex parts like I do it don't half slow down SolidWorks as they get rebuilt every time you make a change. Another thing that gets put in the CAM part is any geometry sketches (with their MAC co-ordinate reference) that you create by expanding the Job Tree, selecting a Geometry then right-clicking and selecting "Generate Sketch from Geometry". I find this feature most useful at times.

For clamps, fixtures etc. I model them up and keep them in a fixture library, drawing on them when needed and adding them to the main Assembly. A word of caution here - once you have added the fixtures to the main assembly CLOSE DOWN THE ORIGINALS WITHOUT SAVING. This is because SolidCAM has a nasty habit of rewriting all the references of parts used in the main assembly so that your originals are now referenced to the clones that SolidCAM created in in the folder for that CAM part.

However, things get complicated when it comes to Turning (and you'll have to bear with me as the SolidCAM turning module is not my strong point). When you define a CAM part in the turning and you select "envelope" or "outline" for the target geometry SOlidCAM puts the resulting skech in the CAM part. It is also the place where the Stock sketch ought to live, whether you have draw it yourself or SolidCAM did if you selected one of the auto stock options.

This is the beginning of a very big subject

The PRT file is simply a file that lists all the references to the main assembly and tracks if any changes are made to the Seed Part thus forcing a synchronisation.