How do I stop all objects from scaling? I'm new to Blender and making a scene with a few objects in it. Somehow I switched something on and all of my objects are scaling and/or moving when I adjust one thing. How can I turn this off? I don't think anything is grouped.

Here's a quick video of the problem.
press O then scale it will work just fine 
you are enabling proportional editing 
make sure you  turn it off