The acre is a unit of area and is used in the imperial and US customary systems with the symbol a.
It represents the area the size of one chain by one furlong (66 by 660 feet). This is exactly equal to 10 square chains, 1⁄640 of a square mile or 43,560 square feet.
It is generally used to measure the size of land.
The are is a unit of area and is a non-SI but metric unit with the symbol a.
It measures exactly 100m² which is the equivalent to 0.0247 acres.
The are is the principle unit for measuring the size of land across the world.