There are three stages to knife sharpening: honing, or steeling, stone sharpening, and professional grinding.
Honing, or steeling, is the act of realigning the edge of your blade. Your knife blade comes into contact with objects and surfaces stronger than itself all the time: counter (!), bone, stones/pits, and so on. This bends the edge of your blade, making it dull. Honing your blade on a steel helps readjust the bent-over parts of your blade so the edge is straight. It’s a good idea to hone your knife before working with it, especially if you keep it in a drawer (which you really shouldn’t anyway), and every 15-30 minutes of continuous use depending on what you’re using it for.