LightShot is an easy-to-use screen capture tool.
Once running, you can call up LightShot at any time by pressing PrtSc. By default you must then draw a freehand rectangle around the area you'd like to capture, although there's also an option to grab the full screen (double-click your rectangle, or right-click and select "Fullscreen").
Basic drawing tools allow you to customise your capture with lines, arrows, rectangles, highlights and text. It's all a little limited - these are bitmap edits, not vectors, so you can't select and manipulate them later - but works well for simple tasks.
Once the editing is done, you can save an image, copy it to the clipboard, or print it with a click or two.
LightShot's real advantage comes in its web options, though. There are tools to look for similar images online, share your grab via social networks (Twitter, Facebook, Pinterest, VK), or upload them for hosting on prntscr.com (you'll immediately get a link to share them with others, no account required).
LightShot is short on capture types (it can't grab the active window). The editor is basic, and you can't prevent the program taking over the PrtSc key. It's free and easy to use, though, and is great for sharing captures online.