Euclidean Geometry is the Geometry of flat space.
It is based on the work of Euclid who was the father of Geometry.
He proposed 5 postulates or axioms that are the foundation of this mathematical branch of Geometry.
The 5 postulates are,
It is possible to draw a straight line from any point to any point.
If you have a straight line it is possible to extend in any direction to infinity.
It is possible to draw a circle given any center and a radius
All right angles are equal (congruent).
If you have two straight lines, and a third line crossing them, and the sum of the interior angle measure of the two lines is less than two 90 degrees, then if you extend the lines, they will eventually cross on that side.