What is the purpose of 'rendering effects in to out'?

The purpose of 'rendering effects in to out' is to prepare clips with effects for smoother playback in the Timeline. This process involves creating a preview file for any effects applied to the clips between the specified In and Out points. When effects are applied to clips, especially complex ones that demand significant computational resources, it can lead to sluggish playback performance. By rendering these effects, the software generates processed files that allow for real-time playback without lag, making the editing workflow more efficient. This ensures that editors can see an accurate representation of their intended final output during the editing process, facilitating better decisions and adjustments.