YouTube Playlists are an important tool because they allow you to organize your videos and, most importantly, turn one view into many views. Playlists help you take control of how your videos are displayed and discovered, letting you choose which content appears prominently alongside your video rather than leaving it up to YouTube. They also give you an easy way to surface and share the content that you want your viewers to check out, including your own videos and videos from other YouTube channels.
One of the coolest (but also most underutilized) tools YouTube provides for its creators is the YouTube Creator Studio smartphone app, available for both iOS and Android. Released just about a year ago, this is where YouTube debuted features like real-time analytics and is a very useful tool for managing videos on-the-fly and engaging in comments on your content.