I use them alot, I think they are called "callouts", at least that is what Word and Snagit calls them.
They are located under the drawing menu in the Snagit Editor....funny I had to get One Note to capture this tool bar...seems Snagit doesn't like to take a picture of itself ;-)
[url=http://s1280.photobucket.com/user/offroadfx4/media/Snagit%20Tool%20Bar1_zpsp3elwqud.png.html]
Here are all the possible options:
[url=http://s1280.photobucket.com/user/offroadfx4/media/Snagit%20Callouts_zpsrvzvri8m.jpg.html]
I use them for almost every online transaction to capture the image, make notes on user names, passwords, etc, then store that picture before it disappears because you never know what screen comes next....some give the option to print a full invoice etc, some just say thank you ;-)