A lamp has the potential to illuminate something. What kind of thing it can illuminate depends on what kind of beam it actually projects. The lamp could be bedside, inside a digital projector, in the headlights of a car, or the flash of a camera. Potential becomes actual when the lamp produces a beam of light with enough lumens to light something up. The ink-and-paper pages of this book have the potential to appear too dark to read under conditions of low light. They therefore have in them the potential to be in need of light from a lamp. Potential becomes actual when it gets too dark to read.
A painter places onto a painting layers of paint that are layers of potential: to be a valuable piece of art, to be appraised, sold, insured, guarded, exhibited, photographed, transported, tracked, and recovered if stolen. None, some, or all of these potentials may become actual. Every instance of actual projects the demand for something to be had, or something to be done, which could be projected into markets for services.
The transition from potential to actual is dynamic. A sofa with plush material has in it the potential to get dirty or catch fire. If it catches fire, a nearby fire extinguisher with the ability to cut off flames from oxygen, projects that capacity in the form of a burst of fire-retarding foam. Or, it could be a spray from a sprinkler system. The fire has the potential to grow into a five-alarm blaze and create a deadly situation that is beyond the actual of the on-site systems, in which case fire department responds with an overwhelming force.
What action needs to be performed on an artifact, and what kind of resource needs to be made available to an event, when and where, and for how long, define the demand for action, and the demand for access, or the two primary ways of advertising the job to be done.