What is are?
An are is a metric unit of area equal to 100 square metres. While largely replaced by the hectare for most practical uses, it is still referenced in some European countries for measuring agricultural plots.
What is square inch?
A square inch is a unit of area in imperial and US customary systems equal to 1/144 of a square foot. It is used for measuring small surfaces, printed circuit boards, and product specifications in imperial-based industries.