Right Triangle - Has one right angle (90 degrees)
Acute triangle - all angles are less than 90 degrees
Obtuse triangle - has one angle that is bigger than 90 degrees
These triangles right triangle, acute triangles, and obtuse triangles are all similar they are all about angles.
Equilateral triangle - Three equal sides
Isosceles triangle - two equal sides
Scalene triangle - no equal sides
These triangles scalene, isosceles, and equilateral are all similar because they are all about the sides.