Equilateral Triangle all three sides have the same length.

Scalene Triangle all three sides are different in length.

Isosceles Triangle two sides have the same measure in length.
 

Classifying Triangles by there angles:

Acute Triangle all three are less than 90 degrees.

Right Triangle one angle of the triangle measures 90 degrees exactly.

Obtuse Triangle one angle of the triangle measures more than 90 degrees exactly.