how to embed youtube video in html

<iframe width="420" height="315"
src="https://www.youtube.com/embed/tgbNymZ7vqY">

</iframe>
 <iframe width="420" height="315"
src="https://www.youtube.com/embed/tgbNymZ7vqY">

</iframe><iframe width="560" height="315" src="https://www.youtube.com/embed/videoseries?list=PLQGSXoAiT2W4W8D3397nl4OB_GxfOmJk9" allowfullscreen></iframe>