Everything is composed of energy. There is physical energy and then more subtle energy. Not all energy can easily be seen. For example, gravity pulls an object to the earth, but you can not see it. Magnetic force pulls two opposite poles together, but you can not see the pull between the two objects. You can see the outcome of a magnetic field when iron filings move along a plane in response to a magnetic field, but prior to the iron filings being there, you can not perceive it. Light is energy - different colors are different wave lengths of energy.
The Human Energy Field
Humans have an energy field around their bodies. The field can be measured. Any electrical activity in a direction creates a field, and you can see the electrical energy in a direction in the brain and body when you see nerve impulses fire, or brain waves appear on an EEG, electroencephalograph recording.
Ancient wisdom from various traditions teaches us ways to protect and care for our human energy fields. As these practices are not yet proven by evidence based science, you may try them in an experimental manner. Try a practice one day, and see how the day goes. Try not doing the practice another day, and see how that day goes. Notice if there is a difference, or no difference, when you use the practice.
Below are two core sacred ancient practices to try with clear intention: