Importance of using YouTube Playlists
If you are creating a video series then I would recommend adding the videos in a Playlist.
Playlists work very well when you are promoting a group of videos as a course or a group of videos on an interest. So each video will then be a separate sub-topic of the main topic or a lesson.
To help promote my videos in the playlist or series of videos, I link the next video of the sequence and the playlist in the end screen. This helps to generate click-throughs and engagement to the next video or the playlist. I also promote the playlist at the beginning of the video and show a Caption for my views to visit. Maybe your audience will want to watch from the beginning of the course or sequence.
To help promote your playlists I add the playlist to the front page of the YouTube channel and call the course. We have segments on the channel called mini-courses and we list each playlist.