what codes used to insert video in web design

Answer 1

<video controls> <source src="video.mp4" type="video/mp4"> </video>

Answer 2

You can use the <video> tag or the <iframe> tag.
Details and examples:
https://www.w3schools.com/TAGS/tag_video.asp
https://www.w3schools.com/html/html_youtube.asp
https://www.w3schools.com/htmL/html_iframe.asp

Answer 3

<video> and <source>, you should complete HTML course.