Videos can be embedded within your pages or as a featured video on any page. It is important not to add your videos to the media library as this can greatly reduce the speed of your site. Instead it is recommended that you use YouTube, Vimeo, or some other site to host your videos.
YouTube’s instructions provide you with the information you will need to upload and share your videos.
To embed a video on a page, once it’s uploaded, you need to place its URL into the content area or in the Featured Video “add Video URL” text box.
If you make the video a Featured Video it will show up at the top of the page, whereas the embedded videos will be placed exactly where you place them within the page, just like adding images.
For embedded video make sure the URL is on its own line. For example:
Check out this cool video: http://www.youtube.com/watch?v=dQw4w9WgXcQ That was a cool video.
WordPress will automatically turn the URL into a YouTube embed and provide a live preview in the visual editor.