Photopea is essentially a free, web-based version of Adobe Photoshop.
A great feature that Photopea offers is an instructional section of their website where you can read step-by-step instructions on how to use different features of the interface and complete different tasks. Additionally, there are a plethora of free instructional videos on YouTube that explain how to use simple, and complex features of the program.
Photopea will store files locally on your computer but can be connected to your Google Drive for uploading files. Additionally, Photopea saves your working document as a PSD file, which is the same type of file as Photoshop. This means that a file created in Photoshop on one computer could be opened and edited by another person on this program.
Student examples of artwork using Photopea
Students created a drawing using a font chosen from DaFont and used Sharpie markers to outline and colored pencils to blend and create different transitions, hues, tones, tints, and shades of colors in their creations. More information about this lesson can be found under the Graffiti Name lesson.
Personal creations that I have made using Photopea