A rectangle and a triangle are both types of shapes. A rectangle is a flat shape that has four straight sides and four right angles (corners that are exactly 90 degrees). The opposite sides of a rectangle are always equal in length.

A triangle is a flat shape that has three straight sides and three angles. The sum of the angles in a triangle is always 180 degrees. There are different types of triangles, such as equilateral triangles, isosceles triangles, and right triangles, each with its own unique properties.

Both rectangles and triangles can be found in many real-life objects and are important building blocks in many areas of mathematics.