A final walk-through is exactly what it sounds like: a final walk through the property so the buyer can take a last look before closing.It's pretty common practice, but there is a standard clause that should be in the offer to ensure the buyer will have an opportunity to take this final walk-through:
The Buyer shall have the right to inspect the property one further time prior to completion, at a mutually agreed upon time, provided that written notice is given to the Seller. The Seller agrees to provide access to the property for the purpose of this inspection.
Although the standard wording refers to it as "inspecting" the property, it is important to note that this is NOT a condition, like a home inspection condition, so there is no automatic right to cancel the deal. But it does provide an opportunity to make sure there have been no significant changes to the property. If there was some major new damage or issues revealed, the buyer would want to immediately discuss the situation with their lawyer.
This opportunity to revisit the property is also often used by buyers to make some measurements for new furniture or renovations they have decided to do in between when they made the offer and closing. Unless it is a short closing time frame, I usually write the clause in to include "two further times" so that buyers can take an opportunity to measure if they need to make orders sooner, and still be guaranteed a final walk-through closer to actual closing.