Thumbnails are the images that you can place in front of your video and can help introduce your video content prior to the viewing watching. Take a look:

You will see to video side by side in Canvas, the one of the left has a thumbnail the one on the right does not. You can use thumbnails to bring more to your videos with minimal time and maximize the appeal.

Canva is a great tool to help you select, create, and download thumbnail images for your youtube videos. You can search for premade thumbnails, then modify the thumbnail using different color themes, images, fonts, etc. Once you have made your thumbnail download the file as a JPEG or PNG file. Now that you have created a thumbnail, log into your youtube account, selecting the video you want to add the thumbnail to, and upload the thumbnail on the edit screen.  Be sure to hit save changes. Now take a look at your video and the hard hitting thumbnail you just created for your video.

If Canva is overwhelming you with options, no worries. Try using Google slides to make your Thumbnail instead. Add and modify anything you want in a slide, then download your slide as a JPEG file.

Thumbnails are just a small way to elevate you videos, especially when you have them embedded in Canvas.