First of all, rectangles and rectangular prisms have one foremost difference, which is their dimensions. A rectangle has two dimensions whilst a rectangular prism has three. Those dimensions include width, length, and height- but a rectangle has only width and length. Although, in comparison, they're both made from the same quadrilateral: rectangles. A "2D" rectangle has one, while a "3D" rectangle, or rectangular prism, is made of six. The rectangles that make up a rectangular prism can also be referred to as faces.
