If I need to do a screenshot, I usually Alt+PrintScreen to capture the window, and pop open Paint to crop it if I have to. Many websites and applications (eg Imgur and Discord) support pasting raw image data from the clipboard as well, which is handy.
For more serious stuff, I use OBS to capture my game window or specific applications, and if needed, use XMedia Recode to fuff with the file formats, but most sites are pretty good about sharing .webm files now.