Both. Meditation is a process of placing your attention, where you choose, in the moment (instead of letting your mind make that decision for you), and focusing and relaxing your body, on purpose.
There are many types of meditation and some are spiritual, while some are secular.
Spiritual meditation: A process of relaxing the body and mind and focusing on a part of the self that feels a connection with every other thing in the universe. This process transcends religion and seeks the experience of something greater than just experiencing the self.
Secular meditation: Just as you exercise your body, meditation is exercise for your mind and brain. You train your mind/brain to focus and relax when you choose so that when you are under stress, you can more easily return to a focused and relaxed state of being. You make better decisions and react more quickly when you are focused and relaxed at the same time. Tension causes constriction in the body (limiting movement and blood flow and draining your muscles of energy) and limits the mind by keeping you stuck in a fight or flight, reactive state. When you release tension in the body and the mind, you can access your creativity, the executive function of the brain, and create a feeling of centered calm between stimulus and response (giving you more control over your response).