Euler Line: Given a triangle, if you draw the centroid, circumcenter, and orthocenter you will find the three points are collinear. (In a straight line)
The collinear line created from these three points is called the Euler line.
The centroid is always located between the circumcenter and the orthocenter.
A centroid is the intersection of the medians of a triangle. A median is a line drawn from the vertex to midpoint of the opposite side.
The orthocenter is the intersection of the three altitudes of a triangle.
An altitude is a line drawn from the vertex perpendicular to the opposite side.
The center of a circumscribed circle about a triangle is the circumcenter.
It is created from the intersection of the perpendicular bisectors of the triangle.