A converging (convex) lens bends parallel light to a real focal point, so it can make either a real, inverted image or, with the object inside the focal length, a magnified virtual one. A diverging (concave) lens spreads light out, so it always makes a virtual, upright, diminished image. Switch the lens, slide the object, and trace the principal rays to see where the image forms.
Choose the lens, set the object distance, predict, then check.