The easiest way for someone to take a screenshot on Windows 10 is to use the Windows key+S. This will darken your screen with a transparent overlay, and your cursor will turn into crosshairs. Take your cursor and drag over the area that you wish to screenshot, that area is now copied onto your clipboard and can be pasted into a Microsoft paint document, word document, PowerPoint, or any other document which allows you to paste pictures into.
Some more up-to-date versions of Windows 10 now include a sniff and sketch tool. You can find it by searching your start menu. When you open it up you can click “new” at the top and your desktop will turn into the same transparent overlay in your cursor back into a crosshair. The advantage of this program is it takes the screenshot and displays it directly in your window. From there you can click the save icon or copy at the top. This will allow you to either save it as a JPEG or copy it to your clipboard to paste in another document.