I picked up this phrase “left of the line” from my friends at the e-commerce site kbb.com. At the highest level, creating software products involves figuring out what to build, and then building it. This line distinguishes those two fundamental activities. Note that this line exists whether you use conventional product development processes or an Agile/Scrum process, although the nature of the line is different.
Opportunity assessment and product discovery is what happens left of the line, and the sprints (implementation and test) and deployment is right of the line.
The product manager is fundamentally responsible for the left of the line (working with user experience and a lead engineer), and the engineering organization is responsible for the right of the line.
When I talk with companies and explain product management and design in conventional and Agile processes, I typically end up drawing out on a whiteboard the key points, activities and milestones. The process that these diagrams represent is discussed in the articles:
There are some very important differences between how product discovery is incorporated into Agile and Conventional processes, but it’s also true that the role and importance of product discovery exists in both.
I’m hoping that you can take a look at the process diagrams and see if this doesn’t shed some light on the key points. This is especially important if you are moving to Agile and you are struggling with understanding how the roles of product management and user experience design fit into this process.