What describes a triangle with three congruent sides and angles?

An equilateral triangle is defined as a triangle that has three sides of equal length and three angles that are all equal, specifically each angle measuring 60 degrees. This uniformity in side lengths and angles is a distinctive property that categorizes it specifically as equilateral.

In contrast, a scalene triangle would have all sides of different lengths and therefore all angles would also differ, making it impossible for it to meet the criteria of equal sides and angles. An isosceles triangle, while having at least two sides that are equal, does not possess the characteristic of all three sides and angles being congruent. Finally, an acute triangle refers to a triangle where all angles are less than 90 degrees but does not specify the lengths of the sides; therefore, it could be scalene, isosceles, or equilateral.

Thus, the defining characteristics of an equilateral triangle make it the correct option for a triangle with three congruent sides and angles.