Embedding is the process of taking an already established product (like a video, a calendar, a map, or more) and placing it on your site so that it appears right in the website. As an example, I embedded the following YouTube video.
To do this, I clicked on "YouTube" under Google embeds. You can upload a video that you have created, or you can search for one. I searched for how to create a Google site using the new Google sites. I found a variety of videos which have already been created. I chose the one that was created in 2017, since this is a new product. I clicked on the one that I wanted to embed, and chose "select". And here it is! To view, you click the forward arrow. You won't be able to view the video until you publish the site. After publishing, click on view.
When the video pops up, you can modify it by clicking settings. Click on the "gear" icon to view the possibilities. Note, you can also resize the window by clicking on the edges and pulling.