Screenshots are the images that are stored in your clipboard memory when you press Print Scrn Button in Your Windows computer or when you press CTRL + Command + Shift + 3 on your MAC computer, it would catpure the Screen being displayed at that time in your Clipboard.
And Today I found an interesting Adobe AIR application ScreenTweetr that can help you share your screenshots either of any website or your local Computer Desktop with your followers at Twitter. Once you have installed this application on your computer it would detect Screenshots captured through above commands and would take you to popular Twitter Image Sharing site TwitPiC and where you only need to enter your current Twitter username and password and upload the image and the image you uploaded would be automatically tweeted in your timeline. Pretty simple eeeh ! :}