This information applies to Pinnacle & Avid Studio which runs on iOS.
Rendering, in this context, is the process of “flattening” your multi-layered effects into one video stream while in the project editor. Without said effort, your device is effectively trying to process each stream separately, and this could easily bog down your performance. By rendering, you simplify the playback, and therefore improve its quality in both accuracy and smoothness.
The render time varies and is dependent on the complexity of your project. The more complex the render, the more time is needed.
Note that rendering automatically occurs on export – there is no need to “pre-render” your project before selecting one of the sharing options.