Let's look at the elements of an envelope. We can use that as a metaphor for how the building works. On the outside of a mailing envelope, we have a return name and address, so everyone knows who we are and where the envelope is coming from. Think of that as the building's street address and the signage.
Next, we put a send-to address on the envelope. Think of that as an invitation, a way to attract specific guests into the business by exterior colors, architecture design, and maybe awnings.
The envelope must be strong and durable enough to withstand the elements, just like the building's foundation, floors, structure, and roof. An envelope has to have ways to get in and out yet be secure; the building's doors and windows serve the same purposes.
Finally, the envelope has to be functional. Its job is to hold the contents and safely cradle them. The building's function is to hold all the furniture, fixtures, and equipment (FF&E), electrical and plumbing systems, and the staff/guests. Though the building envelope will likely never be moved or mailed, it has to preform many functions and requires skilled hands to keep it in peak operating condition. It will present problems that will not always be easy puzzles to solve. As facility manager, a fundamental understanding of the various systems will help you to solve building problems you encounter. Using a process of elimination and choosing appropriate investigation methods, you'll be more likely to succeed in determining a corrective action.