A great many of the spells here are, in fact, fake. Obviously, a spell to control the elements, weather, those that claim to turn you into an animal, etc are fake.
There are many definitions on what magic is, but I will give you my definition. Magic, in essence, is energy. It is an unseen, untapped form of natural, spiritual energy that flows within us and around us.Magic can be used to help you reach realistic goals or to get closer to nature and your higher, spiritual self.
Magic is ruled by scientific law. Meaning, if you can't do it with science or other natural means, then you can't do it with magic.
To use magic, you first need to understand how it works. As previously stated, it is energy within nature. We can manipulate this energy and send it out into the universe to bring things to us, change aspects within us or in those around us, heal, protect, etc. The most common way that this is done is through focus and visualization. For example, if I were working toward the goal of healing someone close to me, I would focus on them being healthy and happy. I would then raise energy within myself (common forms of energy raising include chanting, dancing, or drawing in energy from the world around you.) I would then take that built up energy and send it out into the universe to bring about my goal. As I sent this energy out, I would visualize the ill individual receiving it and using it to speed their healing process.
All that being said, you can use spells you find here, as long as they are real. Making your own may offer you better results, as they have more meaning to you and have been fine tuned to fit your own personl goal, as opposed to something someone else wrote. However, if they are something like the fake spells, I mentioned, you will not get results. Something I always tell new members is this: Common Sense is your friend. Use it wisely.