The parties of course know which house they are talking about but legally it could be any one of a number of properties. Problems arise especially when the land is large or when a stream or wood obscures boundaries. In France one property may often be made up of several smaller pieces of land known as parcelles. Make sure you are certain of how much land is included in the sale and check the boundaries with a 'Plan Cadastral'. Also check if there are any rights of way.
Farmers are no respecters of boundaries.
If there are several buildings, even small sheds, a garage or barn ensure they are all included in the contract. Do make certain that all you see on the land is included in the contract and built with planning permission. When buying a home in England a purchaser receives a full list of fixtures and fittings. In France this is not necessarily the case, so make sure everything is listed in the contract. Leave nothing to chance.