I dont quite get professional video cameras. If they run on video tape then how do you edit movies on the computer? Is there any pro cameras that run on electronics such as SD cards?

professional cameras use a digital format stored to tape....and even some consumer level digital video cameras record to tape. in these cases, the video is transferred digitally from the camera and stored to the hard drive, and it's usually done in real-time because of the limitations of tape.most professional applications don't use flash-based storage because of the size limitations.