 So now we introduce capacitors. What is a capacitor? It's an electrical device, specifically one which is used to store electrical charge. Now when it stores this charge, it also stores some energy. So storing that charge can then be used later on to release some energy. Now typically, a capacitor is going to have two different conductors with opposite charges stored on each one. And those two conductors are going to be separated by a small distance. This is a typical setup, not always the case. The most common type that we discuss in basic physics is what we call a parallel plate capacitor. And in this case, I'm going to have two separate metal plates or some other type of conductor. And they're going to be separated by some distance d. Now I'm going to store positive charge q on one side and negative q on the other side. And when this happens, this is going to establish an electric field between these two plates, going from the positive plate towards the negative plate. So this is sort of a general schematic diagram for the very, very common parallel plate capacitor. We'll study it in more detail later. Here's kind of a 3D view of this parallel plate capacitor. So you can see a little bit more that these really are flat plates. So each one of these two plates has a plate area of A. And the two plates are separated by a distance d. Now for this diagram, it shows a material called a dielectric in between the two plates. But you could also have just empty space in there. We'll look at the dielectric case later. Now parallel plate capacitors are not the only type out there. And here's just a variety of images of a bunch of different types of capacitors. So they come in all different shapes and sizes. And inside all those devices, they could have all sorts of different configurations in them. The important thing to remember is that it stores charge in an electrical circuit. So that's what a capacitor is. Now we can move on to actually studying about some of the equations associated with it.