These objects all have three properties:
A number of shapes within them (1-3), a color (red, black, or brown) and a shape (circle, line, or square).
For a set of three objects to be valid these three properties have to be either all the same or all different.
E.g. these are valid:
One red square, two red lines, three red circles.
They are all the same color, each number is different, each shape is different.
Two black squares, two red lines, two brown circles.
Different color, same number, different shape.
One red square, two black lines, three brown circles.
Everything different.
Two brown lines, two brown lines, two brown lines.
Everything the same.