Solution knowledge is about the knowledge and experience a business analyst has within a particular solution space. In some cases, a business analyst may have gained previous experience when working within a specific solution arena, which becomes a strong core competency to assist them in their next, similar initiative. 

Let's consider a real-world scenario.

If a business analyst worked on an initiative to implement a new gift card solution for a retail organization, they would have gained strong solution knowledge as part of this initiative. When they decide to move to a new role in a new organization, they can make a valuable contribution to a similar initiative where a new gift card solution is implemented by drawing from the solution knowledge they gained in the previous role. By utilizing their existing solution knowledge of the gift card domain, they will save themselves (and their new team) significant time and effort in terms of analysis and research of potential vendors or technology solutions in the marketplace.