Energy work is a form of
magick in which the focus is on
visualizing metaphysical energy and
manipulating it with one's mind. Sometimes tools, such as dancing, chanting, or physical tools such as an
athame can be used to enhance
focus, but they are only to assist. The more essential the caster considers the tools to be, the more the act resembles
spellcraft. The line between the two can be very fuzzy.
Psychic powers, such as ESP, speaking to the dead, weather sense, or clairvoyance, can be considered a form of energy work, because tools are usually not used (with the exception of most forms of divination).
I must point out that energy sense is NOT always visual. Some people might sense vibrations or even sound; others might feel it as in empathy; still others simply sense it intuitively (ie, they know what it means without picking it up through a sense first; this is often the case with psychic powers). In such cases, people often don't realize they can sense the energy, because they can't describe it. Often they say they are just reading body language, for example, which is certainly possible but not necessarily true.
Energy work is not just about perception; it's also about affecting the world around you. It can be used to alter emotions (make sure to have permission before you do this to someone else), protect yourself and your things (ex. from theft), and even alter the weather (but realize that even a tiny change will have far-reaching effects that you can't possibly predict; see chaos theory). My most common use of energy work is to keep my bike from getting stolen when I don't want to lock it; I simply imagine a pentagram in the air, then see it coming down to form a net over the bike.
Sensing and working with energy can be learned, and I think that everyone can learn it (although this can be more difficult if they do not sense it visually, because most teaching styles are visual and thus don't work for them). Practicing without actually doing magic can be done through games, such as energy baseball and energy catch.