In a sexual context, the term edging refers to bringing yourself (or someone else) to the point of orgasm but then postponing the orgasm by stopping, slowing down, or changing up the kind of sexual stimulation.
In most cases edging is described in masturbation, where you pleasure yourself just to the point of orgasm but then pull back. Then you ramp up the stimulation again to the point of orgasm and again pull back. When you do finally let yourself go over the top, many people describe the orgasms as especially intense.
Edging could be done with any sexual activity, but proficient edgers usually say that using your hand for stimulation gives you the greatest control. One of the wonderful things about edging is that it requires you to pay very close attention to your sexual response, or if you’re doing it with someone else it means you have to be very tuned into your partner’s response.