A rectangle is always a parallelogram. This is because a parallelogram is defined as a quadrilateral with both pairs of opposite sides parallel. A rectangle meets this definition perfectly, as both pairs of its opposite sides are parallel and equal in length.
Additionally, a rectangle has four right angles, which is a specific property that not all parallelograms have. However, this does not disqualify it from being a parallelogram. Instead, it makes a rectangle a special type of parallelogram.
In summary, every rectangle is a parallelogram, but not every parallelogram is a rectangle. This relationship is similar to how every square is a rectangle, but not every rectangle is a square.