Before the advent of Title Insurance it was common for a purchaser of a single family residence to obtain a survey to ensure the home and any outbuildings were located within the boundaries of the lot. A survey used to be a requirement of the lender before providing a mortgage.
Now a lender will usually accept title insurance instead of a survey. Title insurance will compensate the lender if there is an encroachment or other defect on the title of the property but it will not necessarily compensate the purchaser. Because of this it may still be prudent for the purchaser to obtain a survey particularly if there is any concern regarding whether or not the buildings are located within the boundaries of the lot.