What is a survey and what is the purpose?
A mortgage survey or "plot plan" is a document outlining the boundary lines, easements, and building setback lines of a parcel of land. It will also likely note any improvements (such as sheds, buildings, fences, decks, pools), natural landmarks like roads, streams, beaches, bodies of water, and any encroaching improvements of the abutting property.
A survey is used to clearly identify the property for the lender's title insurer, and can also be useful to the homeowner in preliminary planning of any further improvements. In many cases, a survey is ordered by the attorney or title company handling a purchase transaction.
A more in depth type of survey, sometimes called a "stake survey" involves the actual physical documentation and demarkation on site. This type of survey is more costly, would only likely come into play when building on an unimproved lot, rezoning, subdividing, or when there is a conflict between abutting property owners.