Layers
If you've worked with programs like Photoshop, you should be familiar will the concept of layers. Basically layers are elements that stack on top of each other.
For example, if you want text to appear on top of an image, you would create a layer for the image, then another layer for the text. Then you would move the text layer above the image layer.

Layers can be one of a few types, a scene, a display or an effect.
Displays
Displays are graphical elements that appear on the stage. They can be static elements such as images and text, or audio-reactive elements like the bar spectrum and soundwave display.
To add a display, click on the Add display button in the layers panel.
Effects
Effects are graphical elements that affect the displays. They are always rendered on top of the displays.
To add an effect, click on the Add effect button in the layers panel.
For example, if you were to add a Blur effect on top of your layers, you would get the following result.

You can add multiple effects and they will be rendered in the order they are displayed. You can redorder effects for different results.
Scenes
For more information about scenes, see Advanced > Scenes.