A rectangle or, if the squares are allowed to overlap it is possible to have a 16-gon ("star" shaped), 14-gon, 9-gon, 8-gon.
There are quite a few. Circles, squares, triangles...
A prism.
a rectangle
Squares.
rectangle
When two squares share a common side, they can be combined to form a larger shape known as a rectangle. By aligning the shared side of the squares, the resulting shape will have two pairs of equal sides and four right angles. This new shape will have a different area and perimeter compared to the individual squares.
A cuboid or a rectangular prism.
Rectangular prism
A triangular prism
If the squares can be placed on top of one another, they could form a shape with from 6 to 16 sides.If the squares can be placed on top of one another, they could form a shape with from 6 to 16 sides.If the squares can be placed on top of one another, they could form a shape with from 6 to 16 sides.If the squares can be placed on top of one another, they could form a shape with from 6 to 16 sides.
There is no solid shape with exactly four squares and no other faces.
A shape made from four rectangles and squares can take various forms, but one common configuration is a rectangle composed of two rectangles stacked vertically and two squares placed side by side on either side of one of the rectangles. Alternatively, you could arrange the rectangles and squares to create a larger square or a more complex geometric shape, depending on the dimensions and placement of the individual components. The specific arrangement will determine the overall shape.