The key difference is:

Euclidean triangles have angles summing to exactly 180 degrees.

This is a property of flat, two-dimensional surfaces. In contrast:

Spherical triangles (triangles on the surface of a sphere) have angles summing to more than 180 degrees.

Would you like a detailed explanation?

Here are five related questions to further explore:

1. How do the sides of a spherical triangle compare to those of a Euclidean triangle?
2. What happens to the sum of the angles in a spherical triangle as the area of the triangle increases?
3. How are the concepts of parallel lines different in Euclidean and spherical geometry?
4. Can a triangle on a spherical surface have all right angles?
5. What is the significance of great circles in spherical triangles?

Tip: In non-Euclidean geometry, the sum of the angles in a triangle varies depending on the curvature of the surface.