Kindle allows you to highlight text in a paragraph/passage you find interesting while reading, which you can then at a revisit later time. You can find the screenshots in the root directory. Now, to access these captured screenshots, connect the Kindle to a computer, and copy the images to your machine. For this, tap on the opposite ends of the display, like the top-left and the bottom-right simultaneously, and it will take a screenshot, with a flash to notify the screenshot capture is successful.
Similar to how you take screenshots on your mobile phones, tablets, or laptops to capture things that come across as interesting, you can also do the same with Kindle.
