Identify the types of triangles based on side lengths.

The correct answer focuses on categorizing triangles based on their side lengths. Triangles can be classified as equilateral, isosceles, or scalene based on how many sides are the same length.

An equilateral triangle has all three sides of equal length, which also means that all three angles are equal, specifically each measuring 60 degrees.

An isosceles triangle has at least two sides of equal length. This property also means that the angles opposite the equal sides are also equal.

A scalene triangle, in contrast, has all sides of different lengths, which means all its angles are also of different measures.

This classification based on side lengths is fundamental in geometry, as it lays the groundwork for understanding more complex properties of triangles, such as angle measures and area calculations. Other options include classifications based on angle measures, such as right, obtuse, and acute, but these do not pertain to the side lengths of the triangles specifically. Hence, the choice highlighting equilateral, isosceles, and scalene triangles is the appropriate one for the classification based solely on side lengths.