Sometimes you don’t want to connect to any particular connection point, but to the edge of a shape. And perhaps you want one end of a connector to move and the other to stay in one position. There are two types of connections, indicated with blue and green frames in draw.io.
If you draw additional lines between shapes in a diagram, they won’t move with your shapes when you move them around the drawing area. By using actual connectors (not lines), your diagram becomes much more flexible and easy to work with. There are four different ways you can create connectors between shapes and quickly extend your diagrams in draw.io.