Geometry typically follows a first course in algebra. Geometry may be taught either as a proof based course or a non proofed base course. The proof based course is offered to help a student develop a logical way of thinking and is typically more difficult and more rigorous then the non proof based course. Geometry was known by the Egyptians in ancient times and was formerly taught by the Greeks under the tutelage of Euclid (325 BC - 265 BC).
A good foundation in geometry will teach you properties of circles squares and other shapes. Each shape has formulas which defines its properties.
The Square: Perimeter = Two times the length plus two times the width
The triangle area = 1/2 times the base times the height
And there are many other formulas for many other shapes