If you want to use a line that links two shapes together, you may then want that line to be always linked, even if move the original shapes. This sort of linking is called connecting shapes. And to keep these shapes connected, you most certainly will start by drawing a connector instead of a normal line. A connector looks like a line, but it stays connected to the shapes you attach it to. There are three types of connector lines: Straight, Elbow (angled), and Curved.
Learn about different connector types in PowerPoint 2013 for Windows.

