The cadastre is the record that each province keeps of how its territory is divided. The parcel is its unit: a polygon with defined limits, a number that identifies it and an associated tax valuation.
It is the legal definition of property, and that is why it is the most reliable starting point for calculating a report: choosing the parcel from the cadastre avoids the errors of drawing the perimeter by hand and guarantees that the surface is what appears on the papers.
There is no national cadastre: each province maintains its own and decides how much it publishes. This causes the same click to return different things depending on where it lands. Córdoba is the only one that publishes the tax valuation and the declared meters built. Neuquén is the only one that says if the plot is built on. Misiones and San Juan publish the polygon and nothing else, so there we calculate the surface on the perimeter and say it.