Dependency vs Project Impact - what is the difference

Hi Dave. A progress impact is an advanced function that lets you make a relationship between work items that is very different from a dependency. Let's say you want to make a summary milestone that is a roll-up of 3 different milestones throughout the project. One of the milestones you want to have 50% of the impact on the summary milestone, while the other 2 milestones only have a 25% impact. You would do this with progress impacts. As those milestones are being completed, they are impacting the % completion of the summary milestone based on their weights. Progress impacts have no impact on scheduling at all, they only affect how % completions are calculated.

Josh Hello
Please explain a bit more on the summary milestone, how would it be placed - within the same hiearchy of the 3 sub-milestones?
I understand what you explained above, and I am excited to use this ability, would the 3 rollup milestines be place top to bottom in sequential order and further down the plan would be the summary milestone- from the tuturial I understand the main project would contain subprojects- in the subproject it is possible to place the milestones that roll up into the main project's summary milestone - is this exact? - a small screenshot of the way this would work would be most helpful.

You can actually place the summary and rollup milestones anywhere you want (even in a subproject). The progress impacts work similar to dependencies in this respect. Usually I see at the very top of the master project.