When you create a conversion code in ClickMeter as the results you get at least two output, a conversion java-script code and a conversion pixel.
Both perform the same actions and can be used to track conversions.
Please note that sometimes the conversion pixel is also (erroneously) called tracking pixel.
The Tracking Pixel (not to be confused with Conversion Pixel) is a image of one pixel that you place in a webpage or in an email and let you track how many times the webpage has been viewed or the email opened: http://support.clickmeter.com/entries/28182193-How-to-create-a-new-tracking-pixel-video-
The Conversion code is a piece (snippet) of code you place in the thank you page to track conversions. The Conversion Code can ALSO be a Conversion Pixel.