We always need a minimum of two points to create a path, since we need to know where the path starts and where it ends. If we use enough points that we can bring our path back to the same point it started from, we can create different shapes out of paths, which is exactly how Photoshop’s various Shape Tools work. The Rectangle Tool uses paths, connected by points, to draw a rectangular shape. The Ellipse Tool uses paths, connected by points, to draw an elliptical shape, and so on. It’s also how Photoshop’s Type Tool works, although Photoshop handles type a bit differently than it handles regular shapes, but all type in Photoshop is essentially made from paths. In fact, you can convert type into shapes, which then gives you all of the same path editing options with type that you get when working with shapes.
You may also have heard paths referred to as outlines, and that’s a pretty good description of what a path is, or at least, what a path can be. We can draw a square path, and if we do nothing else with it, as in we don’t fill it with a color or apply a stroke to it, then all we have is a basic outline of a square. Same with a circle or any other shape we draw. The path itself is just the outline of the shape. It’s not until we do something with the path, like fill it, apply a stroke, or convert it into a selection, that the path actually becomes something more than a basic outline.
You can select an entire path using the Path Selection Tool (also known as the "black arrow" tool), or you can select individual points or path segments using the Direct Selection Tool (the "white arrow" tool). A path “segment”, or “line segment” as it’s sometimes called, is any path between two points. A rectangular path, for example, would be made up of four points (one in each corner), and the individual paths connecting the points together along the top, bottom, left, and right to create the shape of the rectangle are the path segments. The actual path itself is the combination of all of the individual path segments that make up the shape.