This slide should be included in all cases that an enterprise software product is complementary of a larger set of solutions that encompass the totality of what the end customer should be deploying to run their business. It shows a few things:

Where the company fits into the ecosystem;
How the target company solution might complement the strategic buyer's existing solution;
Which integration points and API interfaces are typically owned by which vendors, and therefore where certain channel lever points and partnership opportunities might exist;

In this hospitality example, the core Property Management System (PMS) offering is represented in blue. Key 3rd party solutions are in green, the Target Co fits into the CRM module. The CRM module itself is most directly complementary of the Central reservation PMS module, and is directly complementary of the 3rd party-provided Revenue Optimization/Yield module; as you'd expect, target list for this company include the PMS vendors, and the Revenue Optimization vendors, as well as all of the more and less obvious players in each of the other boxes.

The solution stack slide not only helps the strategic buyer to understand how a company fits into their ecosystem, it proves that both the company and their banker understand how to articulate the fit.