Square Properties: Analyzing a Quadrilateral with 3-Unit Sides

To determine if the quadrilateral ABCD is a square, we must confirm two simple properties: all sides are equal, and all angles are right angles.

According to the problem, ABCD is a quadrilateral where all sides denoted by $\overline{AB} = \overline{BC} = \overline{CD} = \overline{DA} = 3$. This indicates that all sides are equal.

Visual context and information suggest, despite angles not being numerically specified, that the shape illustrates a square. Typically, when all sides are equal and we assume connecting lines that meet perpendicularly (which a standard square depiction strongly suggests), the angles are $90^{\circ}$.

Therefore, since all sides are equal and it is reasonable to expect all angles are right angles from the context provided, ABCD satisfies the conditions for being a square.

Thus, the quadrilateral ABCD is a square, so the correct answer is "Yes".