Of all of the extensions out there, Capture, Explain, and Send Screenshots is one I use multiple times every day. This extension allows you to grab any portion of a document, website, or screen and then manipulate it with highlights, arrows, or text. It is great when trying to explain something or to highlight a certain portion of text.
Go to your Chrome Web Store and search Capture, Explain and Send Screenshots. Then add it to Chrome and accept permissions.
The extension will be on your toolbar when you sign into Chrome.