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 acre?
An acre is a unit of area in imperial and US customary systems equal to 43,560 square feet. It is the standard unit for measuring agricultural land, property lots, and parks in the United States and United Kingdom.