Well it's a bit complicated so I'll try to keep it simple. Anything you create anything as in arts - music, videos, literature, pictures, coreography and such. Industrial property and patents function differently is considered your intellectual property.
Now you can simply forfeit your intellectual property, then your work is public domain, and people can do whatever they want with it, no restrictions. Now there are certain types of licences that grant similar rights like public domain, like the creative commons licence, but I won't be going into that...
In any other case people are not allowed to use your work for commercial purposes without your consent, otherwise they can face civil liability. The other thing you described is called "fair use". Fair use means that other people can use your intellectual property for purposes such as reviews, education and so on, again mostly for non commercial purposes.