1 Toolbar (Shortcut: ⌘ + alt + T): Used to add components to your compositions and provides several other functions.
2 Library (Shortcut: ⌘ + L): The library shows the content of the repositories which are specified in the preferences of composition:builder. It can be used to quickly add media to your composition.
3 Workbench: The workbench is the visual representation of components. Here you can modify a component's position and size.
4 Timeline: Used to set, remove or modify keyframes, scrub through your composition and to define the components order.
5 Inspector (Shortcut: ⌘ + I): Used to adjust attributes of components and setting composition specific settings.