"Printer friendly" means that something you see on a screen (like a website, email or document) can be easily printed out on paper without any extra stuff like pictures, ads or big fancy borders that might make it hard to read. It's kind of like making a plain, simple version of what you see on a screen that can be printed easily and clearly by a printer. It's very helpful when you want to print something from your computer or phone because you don't want to waste ink and paper on things you don't need, and you want the printed version to look nice and easy to read. So, a website or document that is printer-friendly is basically a version that is easier for a printer to handle and easier for you to read when it's printed out.