Question

what is difference between median, bisector and perpendicular bisector

Answer 1

Median is a line segment that bisects the opposite side of a triangle and divides it into two equal traingles.
Bisector is a line that bisects any line segment.
Perpendicular bisector is the line which is perpendicular to a line segment and also bisects it. In an equilateral triangle median and perpendicular bisector are the same.

Answer 2

The median of a triangle corresponding to any side is the line segment joining the midpoint of that side with the opposite vertex.
if any line segment divide the any other line segment into two equal parts is called bisector of the that line segment.
if an bisector formed the angle of 90 degree on that line is called it's perpendicular bisector