Each website has at least 5 different traffic streams. For each channel of traffic, the users usually behave differently. Sometimes, the behavior is driven by the use of a landing page specific for that channel, or specific promotions, but most of the time the differences in behavior are coming from the core fact that users from different sources land on the website with different shopping "mood".
Shopping funnel by channel grouping report is showing you for each traffic stream you have how the users are progressing thru the expected shopping behavior.
Use this report to find out where you should concentrate your efforts. Look at the completion rate for other channels. See where is the biggest drop-off in the completion rate. In the above example, you can see that for the Paid Seach only 5.7% of the website users ad a product to the basket even though the biggest driver to the product page is exactly this channel. Increasing the add to cart numbers for this channel will automatically increase the conversion rate.
This report is meant to help you reduce the noise but also to analyze the funnels differently.