It is impossible to print a human using a 3D printer, as of April 2015. However, 3D printers are capable of producing models of humans using files created with 3D modelling software and materials such as plastic and metal.
Although it isn't currently possible to print a person using a 3D printer, scientists are experimenting with 3D-printed human organ tissue. This works by using human cells as printing material and then arranging the cells into the appropriate tissue structure as found in nature. The cells connect and grow to create a larger mass of tissue.
A wide variety of figurines, statues, action figures and models can be printed using 3D printed technology. A popular repository for 3D printer files is Thingiverse.com where everything from nuts and bolts to knives and forks are available to download and print.