1. **State the problem:** We have a triangle with side lengths 6 mm, 6 mm, and 6 mm. We need to determine what kind of triangle it is. 2. **Recall triangle types based on side lengths:** - An **equilateral triangle** has all three sides equal. - An **isosceles triangle** has exactly two sides equal. - A **scalene triangle** has all sides of different lengths. 3. **Analyze the given side lengths:** Since all three sides are 6 mm, they are all equal. 4. **Conclusion:** The triangle is an **equilateral triangle** because all sides are equal in length. **Final answer:** The triangle is equilateral.