Components are what fill up your windows with useful content. Anyone familiar with computers should already understand the basic concept of a component - they are the widgets that you deal with every day - buttons, text areas, dropdowns, charts, and so on. The Vision module comes with a host of useful components out of the box, many of which are specialized for industrial controls use. Other modules, like the Reporting module, add more components for specialty purposes.
Configuring components will likely be the bulk of a designer's work when designing a Vision project. The basic workflow is to take a component from the palette and drop it into a container on a window. From there, you can use the mouse to drag and resize the component into the correct position. While the component is selected, you can use the Property Editor panel to alter the component's properties, which changes the component's appearance and behavior.
Shapes are components too. Each shape may be individually selected, named, and has its own properties. Shapes have some additional capabilities that other components don't have, such as the ability to be rotated. Shapes are created using the shape tools, not dragged from the component palette.
To make the component do something useful, like display dynamic information or control a device register, you configure property bindings for the component. To make the component react to user interaction, you configure event handlers for it.