Yes, I know that my computer comes with that inscrutable PrtSc key (Print Screen), which I can use to copy a picture of my entire desktop onto the Clipboard (more info here). But Snagit is better.
- Snagit has a simple interface, even after countless versions (please heed this, Techsmith!)
- You can easily choose what you want to take a picture of (the whole screen, just one window, a region that you draw with your mouse)
- You can do the things you're most likely to want to do with the image you've captured: paste it into an email, save it as a file, print it.
- You can even add stuff to your snapshot, like highlighter yellow or big fat red circles and the words "click THIS BIT RIGHT HERE"
- There are some nice bells and whistles, too:
- capture a scrolling window all at once, rather than screenful by screenful;
- magnify or shrink what you're capturing
- choose what file format you want to save the image as
- automatically name a series of captures
- Illustrating instructions for some process on the computer (e.g. saving Word documents without the prior edits available in them)
- Documenting problems (error messages) or odd behavior of my computer ("See? My monitor has this line of schmutz running across it. That's not right!")
- Printing a web page exactly as it appears, so that I can do a paper-based usability test) or mark it up with edits
- Putting a picture of your website or software in a newsletter or promotional materials
As of this writing, it costs $50, with discounts for education, nonprofit, and government. There's a free trial (fully functional, 30 days), so you can see if it becomes one of your favorite tools, too.