Area

An area is effectively a length times a length

if the units of length are in cm then the area is in CM^2 (squared)

You need to remember the formula's to work out the areas of

Rectangles

Triangles

Circles

Area Rectangle=Base X Height

Area Triangle=Half the Base X Height

Area Circle=Pi X radius X radius (or better known as image below)

For more information try BBC Bitesize - Area and Perimeter