DQ: Yes, there is a difference. To 'save' something to a disk drive means you can access the file again, for example, even when offline. To 'run' software means the application will do what it is supposed to do, but then disappear. Many applications that just run are in fact downloaded to your machine but are then erased after you have run them. This is a common occurrence for videos. Sometimes the site showing you the video does not really want you to save it, but that is usually very easy to get round. Saving something has another advantage in that some files can be viewed or accessed by more than one application. If, for example, you go to a site that has an Adobe PDF file, you may be asked if you want to run or save it. If you select run, your system will always use one particular application to run it. Some people, however, may prefer to use Apple's built in Preview program. If you save it, you have the choice of running or just saving it. The same is true with video files. No matter if you run or save, you should have some kind of system installed that will check software for malicious codes. The internet is not a very safe place anymore.