3D printing is the process in which material is joined or solidified to create a 3D object.
3D Printing is a process in which material is joined or solidified under computer control to create a 3D object. It uses the material in the form of plastic, resin, or powder to do so.
To 3D print, you need a 3D CAD file. This is what tells the 3D printer what to extrude, where to go, thus forming a 3D printed part.
View a short video below that covers the basics of 3D printing.