One of the topics that readers of my Secrets to Mastering the WBS in Real-World Projects-Second Edition book (PMI, 2010 and 2013) enjoy is when I write about the four typical confusions that individuals have about the Work Breakdown Structure (WBS). One of these four is related to confusing the WBS with the activity list. I have asked some project managers: “Do you know what the WBS is?”…and many times the answer I got was: “Ah yeah! the activity list!”…thus demonstrating me that they actually didn’t understand the WBS concept. They may have listened about it, mainly in theory for sure, but they don’t know how to use it as a true and valuable tool in their real-world projects. The WBS differ from the activity list in many ways. Their purpose is different. The timing when you use it is different as well, and there are plenty of other differences. To begin, you create the WBS before you develop the project schedule or activity list. What is more, the WBS is an input to the Define activities process. On the other hand, the WBS belongs to the project scope management knowledge area while the activity list belongs to the time management knowledge area. The WBS defines all the work that the project will deliver, while the activity list and the schedule define the tasks that you will need to deliver all WBS components or work packages. The WBS has to do with the project’s WHAT, while the schedule deals with the project’s HOW and WHEN. You can check out more differences and a deep treatment of this topic in Chapter 3 of my Secrets to Mastering the WBS in Real-World Projects-Second Edition book whose versions are available in print and in kindle. This book is only in English and sold by the Project Management Institute Inc (PMI) in their website STORE at www.PMI.org. You can also find the Kindle edition in www.Amazon.com. Make sure you buy the second edition which is the latest one.