Are you in need of creating some diagrams? You could get free graphics at Pixabay.com and then use Google’s Drawings to create a diagram. The png file below was inserted into this page at its full size. There are two layers to this diagram: the laptop and the text box. The text box sits “on top of” the laptop.
As an alternative try this website. It is free to sign up. You can easily create your own graphic files and then download them for use on your website.