Introduction text is an overlay that appears at the start of the video. This text can stay on for as long as you wish before fading away and helps orient the consumer to the contents of the video.It is also good practice for the thumbnail on socials to have information on what the clip is about from the profile grid.
If you set the duration slider all the way to the right, the value will snap to _Video Duration. _This will result in the text appearing for the entire time on the screen.
A video overlay is used to overlay an image on the entirety of the screen for the duration of the video. Common use cases for this are adding a border around the video or adding a full screen watermark.