Presets are essentially a micro-save of your formatting and effects settings that you have applied to an object that you want to use again on another object. To save a Preset of an object, select the Object, click the Preset dropdown in the Edit Ribbon above the Edit Area and in the top line, type a name for the Preset and hit Enter. The Preset settings window will open and allow you to select exactly which attributes you want to save to the Preset. You can save them all or only a few. To apply a Preset, simply select the object in the Edit Area, then in the Preset dropdown, choose the Preset you want to apply from the list.
Presets are tied to Object type, so a saved Preset for a Text Box can only be applied to other Text Boxes. The same is true for Image Objects and Video Objects. The Preset dropdown list will only show you Presets that are valid for the selected object when you go apply a Preset.
The benefit of Presets is it can save you a lot of time by allowing you to create a formatting look/style that you can reuse over and over without having to go through all the formatting changes with every text box each time.