A triangle that has all angles less than 90° (90° is called a Right Angle)

A triangle that has an angle greater than 90°

A right angled triangle is (you guessed it), a triangle that has a right angle (90°) in it.

Scalene triangles are triangles where each side is a different length. They are unusual in that the are defined by what they are not. Most triangles drawn at random would

A triangle with all three sides of equal length. All the angles will be 60°

A triangle with two equal sides The angles opposite the equal sides are also equal