An orthocenter is the intersection of three:
Altitudes in a triangle.
Altitude--
An altitude is a line segment that originates from a vertex and is perpendicular to the line segment opposite to that vertex.
Orthocenter--
An orthocenter of a triangle is a point where the three altitudes of a triangle meet or intersect.
In a right angled triangle the orthocenter is the vertex of the triangle where the right angle is formed.
