Hi
From a practical point of view and without any project in the works, i.e all previous work completed and exported, open VP and initiate Options/Disc/Clear unused cache files.
This action will delete everything in the cache leaving it empty for any future project. (The VideoPadSoundCache folder however will remain but will also have been emptied.
When you start a new project and load clips/images etc to VP the cache will fill with copies of these. As you work it's a good idea to Save Project AS regularly. It's also useful to have a dedicated named folder for these saves. Each time you Save As use a descriptive or numbered name. You could do this after every editing session, but in certain circumstances do it after an important editing step. These saves will be .vpj files containing data which will enable VP to reconstruct your project. These data will also include the names of the used clips and their location on the computer as well as info relating to any texts you have added and any editing steps you have made; in effect a snapshot of your project at that point in time. Although you may produce numbers of vpj files in the course of a project in this way, each will enable you to "go back" as it were to a previous configuration/editing point of the project. If you elect to save your work with Save Project (no As) subsequent saves will overwrite the previous save and consequently you will only be able to step back to one previous configuration.
So why the need for a cache?
The cache contains copies and TNs of the loaded clips and so when the vpj file is loaded, VP can get the necessary files from the cache instead of having to search the computer for them. It is much faster, As the vpj file contains info relating to the location of the clips, texts as well as all the editing steps it can, on its own reconstruct your project even with an empty cache. But it will take longer..appreciably longer with a big project as it will also have to rebuild the cache.
At any point with a project open on the timeline and you Clear unused files. Things are tidied up. Clips actually in use are kept and anything from a previous project (or projects) is deleted. So, If you are working on several projects simultaneously and for example staggering working sessions don't clear the cache until everything is completed and exported.
Remember that whilst a cache can speed up loading, a huge cache full of redundant files can slow things down.
Nat