A conventional loudspeaker is designed to spread sound over a fairly wide area: it has a paper or plastic cone that moves back and forth, pumping sound in a wide arc in front of it. The more energy you feed into a speaker (in the form of electric current), the more energy it can pump out as sound, the further the sound waves can travel, and the louder they seem to be. Giant speakers used at rock festivals produce so much energy that they can be heard over a huge area, whether you want to hear them or not.
Most of the time this is exactly how we want speakers to behave, but there are times when it would be helpful if they could work more selectively. Suppose you're the captain of a giant, fast-moving warship and you see a tiny fishing boat moored just up ahead and locked firmly in your path. If it doesn't respond to radio contact, you have a problem. You could use a megaphone to try to call out, but that's just a basic loudspeaker, really, and the sound it makes will probably not reach far enough. Wouldn't it be neat if you could send out a very focused "shout," in a tight beam of sound, that would travel all the way to the fishing boat to catch its attention, even from a huge distance away? This is essentially what a directional loudspeaker does: it's a kind of "sound flashlight" that can "shine" sound energy into a precise spot, even from some distance away.