Capturing whole screen:

Press the PrtScn key on your keyboard. Typically this key is to the right of the function keys at the top of your keyboard. Pressing the PrtScn key places an image of your whole screen into your computer's memory. You can now paste the image into an email (rich text or html), word processor, etc.

Capturing the active window:

Hold the Alt key down and press PrtScn key on your keyboard. The Alt key(s) are on either side of the space bar of your keyboard. Pressing the Alt and PrtScn key places an image of the active window into your computer's memory. You can now paste the image into an email (rich text or html), word processor, etc.

Capturing a portion of your screen:

Use the Snipping Tool to capture any part or all of your screen. The Snipping Tool places an image of your screen or partial screen into your computer's memory. You can now paste the image into an email (rich text or html), word processor, etc.