End screens are useful when sharing projects that we have created

You can add end screens to videos...

Here are tips from a page in YOUTUBE

Add end screens to videos

You can build viewership with powerful end screens on your videos, which show on mobile and desktop devices. Use end screens at the end of a video to:

• Point viewers to other videos, playlists, or channels on YouTube
• Call for subscriptions to your channel
• Promote your website, merchandise, and crowdfunding campaigns 

End screens are a part of the video that show during the last 5-20 seconds of a video. You can add up to four elements to promote your content, channel and websites. Elements can expand to show more information on hover on desktop and on tap on mobile devices.

How to use end screens

End screen requirements for viewers

Add an end screen

Note: To avoid a poor user experience, end screens only work on videos that don’t already have standard annotations on them. If you’d like to add them to a video with annotations, you’ll be prompted to unpublish any annotations first. You can republish them if you decide not to use an end screen.

HERE ARE SOME TIPS that appeared on the screen when I first used ENDSCREENS

1. Sign in to the your YouTube account.
2. In the top right, click your account icon > Creator Studio.
3. In the left menu, select Video Manager > Videos.
4. For the video you want to add the end screen to, click Edit.
5. In the top tab bar, click End screen.
6. If the selected video contains annotations, follow the instructions to unpublish them. You can re-publish them at any time.
7. You’ll see your video with the predefined grid and a timeline below that indicates the available part for the end screen. Click Add element. You can add up to four elements, and one of them must be a video or playlist.
8. Choose how to build your end screen:
   
   • Add element: You can add up to four elements to a video. At least one element must be a video or playlist. Select each element and fill in the required information, then click Create element.
   • Copy from video: You can copy an end screen from another one of your videos and edit the elements.
   • YouTube template: You can choose from predefined formats that show combinations of elements. You'll need to define the content for the elements in the end screen, such as add the channel to be featured.
9. Adjust the placement and size of each element on the grid. Adjust the time for the element to show in the timeline below.
10. Click Save.

You can preview the element at any time by selecting Preview on the top left of the player. You can always go back and edit the end screen and its elements.

What your end screen can show

Elements are the pieces of content that you add to your end screen. Some elements can be expanded or hovered over to provide more information. You can add up to four elements in your end screen for videos with standard 16:9 aspect ratio. 

Elements can feature different types of content:

• Video or playlist: You can select to always feature your most recently uploaded video; allow YouTube to select a video from your channel to best suit the viewer; or pick any video or playlist from your channel, public, or unlisted content.
• Subscribe: Encourage subscriptions to your channel.
• Approved websites: Link to your associated website or to approved merchandise and crowdfunding websites. Provide a custom image, title and select a call-to-action.
• Channel: Promote another channel and provide a custom message.

Best practices for creating end screens

• Feature elements that are relevant to the video.
• Encourage viewers to click using calls to action for different end screen elements.
• Make sure you leave enough space and time at the end of the video for an end screen. Make sure you consider the video's last 20 seconds when editing it.
• Consider timing different end screen elements to appear at different times. 

Check end screen metrics

You can check performance of your end screens in YouTube Analytics in your Audience retention report or use the End screens report.

1. Sign in to the your YouTube account.
2. In the top right, click your account icon > Creator Studio.
3. In the left menu, select YouTube Analytics > End screens.

Note: End screens are meant to create powerful end-of-video experiences for your viewers. As the system evolves, we plan to optimize the experience based on performance, viewer behavior, device, and context. There may be instances where your end screen, as designated by you, may not appear. For example, we may skip the end screen when your video is playing in background mode, or adjust placement on very small screens. For these reasons, we don’t recommend pointing to elements or adding crucial content to the end screen part of the video.

REFERENCE:  https://support.google.com/youtube/answer/6388789#instructions