Ground coffee is purely roasted coffee beans that have been ground down. This then needs to be brewed in a very particular way and may take a few minutes to fully brew. At the end of the brewing, you are left with used coffee grounds that need to be discarded. Instant, as implied by the name, has a much faster brewing time since all you need to add is boiling water. What instant coffee is essentially is a dissolvable form of pre brewed coffee that is made in a factory. The process involves making a large batch of coffee from beans, reducing it down to a concentrate, and freeze-drying that concentrate into the crystals we get from the jar. The bonus, besides the time frame, of instant coffee is there is nothing left behind after brewing that needs to be discarded.