The four foundations of mindfulness are based on Buddhist practice, and can be described as follows:
Mindfulness of the body - this foundation teaches us to focus on the physical experience of having a body and all of its parts - eyes that see, fingers that feel, lungs that breathe, etc. Breathe deeply, observe with your senses, and work to feel each part of your body functioning in harmony.
Mindfulness of feelings - this foundation tells us to think about sensations that we might be experiencing, both pleasant and unpleasant
Mindfulness of Mind - this foundation examines our mental state, and any state of mind we may be experiencing, like greed, jealousy, distraction, or constriction.
Mindfulness of Dhammas - this foundation focuses on our existence and humanity as a whole.
This is just a basic outline of the four foundations, and some people spend years studying what the Buddha taught his disciples about mindfulness.