I personally like using TinyTake. I'm sure there are plenty of options out there, but I like having the ability to quickly take a screenshot, record a quick video and email it. It's a huge time-saver for me at work. I work as a CSM at a Saas company so being able to reply with a quick video showing my customers/clients how to do something is great.

Screenrec is super easy to use and amazingly enough, free.

It runs on Windows, Linux and Mac, captures images, works as a video recorder and offers instant sharing.

It's screenshot annotation tool lets you add comments, draw rectangles and arrows or add text.

One option you could use is Microsoft Paint. It includes a menu option to capture a screenshot, and then you can annotate your capture with arrows and text before saving it.

SnagIt is one of the most advanced screen capture tools, though also is pricy. Greenshot is more basic, though free, and does include annotation tools. Or, for something in the middle, Screenpresso has both free and paid versions, and has annotation tools with a more modern design than Greenshot.

I now use a Mac as my primary but on Windows, I have been replying on ScreenshotCaptor for years. It is most definitely not the sexiest of applications but:

• Alll the functionalities I needed are there
• It's fast and responsive
• And it never caused an issue on any of my systems.

Good luck.

Does it have to be free?

Because I recently bought Cleanshot X and it's awesome.
It's not free but a one-time payment of $29.