I need to shoot the clouds and how they are moving during the time. I saw a lot of time similar clips on youtube and always shot it is just a set of animated photos. Am I right? If yes, is there any special name for this approach? Or is it just an accelerated video?
I think what you're thinking of is time-lapse photography. In a sense it is animated photos, except that the "photos" are captured with a video camera.
You can certainly Google time lapse and get hundreds of good ideas for creating time lapse photography, there are two methods for doing it--in-camera, and post-production.
For in-camera, you're generally going to be shooting 1 frame every x seconds. The larger "x" is, the longer the time lapse will last, and the more time between each frame. I usually run some tests starting at 1 frame every 30 seconds and adjust from there. It take a lot of time to test, since you have to go through about 200 frames to get a true sense of what the motion looks like.
In post-production, you would just take the 1hour clip you photographed in real time, tell the software to make it, say 30 seconds, and the software will automatically pick out the frames it'll show you during playback. Again, it's like animated stills, one frame at a time.
The principle is the same: normal film/video is 24/25/30 (depending on your standard) frames every second, you compress the time by INCREASING the time interval between frames. Instead of 24 frames per second (fps), 8 fps will give you fast motion and 1 frame every 8 seconds will move so fast it's a time lapse clip.
Whether that technique happens in-camera or in the post production proceess is up to you.
Your question doesn't really explain what you are trying to do - my guess is that you mean a speeded up film of cloud movement over a long time period.
If so, your two statements are actually the same - a video is a series of photos...
Generally you take a series of individual frames at a low rate (1 a second, 1 a minute or whatever) then play them back at 24 frames a second to speed up the footage into a video.