They are attuning to the energy around them. Spells are like focused prayers. You are asking for a specific event. Rituals are techniques to raise these energies and intents, to amplify them so they occur. We all create our own reality by the thoughts we put out.
Witches are simply more conscious of that process and put out strong thoughts.
Witches also ask these spells harm none and be for the good of all involved. By taking on the power, you take on more responsibility. During these classes I had experiences that were nothing less than mind blowing. They opened me up to the interconnectedness of all things. At first I was just looking for a philosophy, an arm chair spirituality.