Jez Humble posted a blog entry with the same title in 2010, but if you haven’t read the entry, or just want a quick explanation, here’s the short version:
A continuous delivery pipeline automatically tests the application, but keeps the deployment decision as a manual step. A continuous deployment pipeline, on the other hand, will automatically deploy this working version. There is no “right” way. Different organizations have different needs. Use the one that delivers the most value to your customers!