In this After Effects tutorial, Owen Thiel covers null layers.
I'm going to show you how to use no layers. Now, no layers are used to parent several objects to one thing so that you can resize the null layer or null object to not have to worry about the sizing of the other things.
I have two of them here. I'll show you how I'm using them in a second, but first I'm going to show you how to make one. You go to layer new null object, and that just puts one in. If you want to parent an object to it, you'd take this little squiggly and put it into the layer. We don't want that right now, so we're going to undo that and get rid of him.
But say we did. Why would we need it? Well, we would need it because some of these things in the case of this, can't be parented to their own objects because I found that just doesn't quite work out. Things resize a bit inaccurately. But if you parent it to a null layer, I've got one for the first part of my composition, and one for the second, they resize all of the objects and this invisible layer resizes with them. But you don't have to worry about that. See, I'm putting up the scale. It's getting bigger, everything, even the stuff off-screen. I'm moving the position. It goes away.
Yeah, that's how you use null layers, and that's why you'd want to use null layers.