Teh term "Farm" is used to describe an arbitrary group of computers (usually servers). When you apply a noun like SQL, Windows, Exchange, SharePoint, etc to this use of the word "farm", it implies that all of the machines in the group are running the named application or are used to support that application (such as a domain controller in a farm).
This isn't common usage for the word "farm" in the last fifteen or twenty years, which makes it difficult to Google... The meaning can often be colored by historical usage, so you probably want to clarify exactly what your boss means.
In theory, theory and practice are identical. In practice, theory and practice are unrelated.