Generally, the actual app is not moved, just some app data. That being said, apps "moved" to the SD card will still run, since the location of the data (and, for the most part, the app) is invisible to the user. The apps still show up in Application manager and the app drawer without regard to whether they're on the SD card.
In my experience, you really don't gain that much by "moving" an app to the SD card. Now, if you only have 4GB of storage than, yes, every MB counts but on devices with more storage saving 10MB by moving an app to the SD card doesn't do much. Heck, even if you moved 20 apps and saved 20MB each that'd only be 400MB saved. ...not sure it would make much difference in the long run and it may cause lesser performance (in launching those apps).