ShareX

ShareX is a screen-grabbing program. It allows users to get screenshots, but then do quite a bit of editing to that file. The program offers an impressive array of filters, graphics, and more. If you want, you can even add your own watermark to a file. Once a file has been edited, it can be saved and shared anywhere. It also comes with very, very extensive annotation tools, making it easy for you to note something that is happening on your screen.

ShareX is completely free to use. As an open-source program, it was developed for free use. If you want, you can access the source code on your own. It's also worth noting that ShareX has also been in development for over 12 years, so its developers have ample experience in the area and at improving the program.

ShareX has an extensive website that lays out the numerous great features that the program has to offer. This includes the various methods of capturing and the tools that can be used from the website. As you may expect with a program like this, simple screenshots are easy to grab, but more complicated features take more time to understand. However, this shouldn't stop you - particularly considering that the program is completely free. Furthermore, the website lists a variety of support resources, and you can always reach out directly to the developers.