3D printing is a technique that creates three-dimensional objects from digital models. 

Here is a simple explanation of how it works: 

• 1. Digital model: First, a 3D model is created on the computer. This can be done with special software or you can use an existing model. 
• 2. Preparing to print: The digital model is then translated into a language that the 3D printer understands. This involves breaking the model down into many thin layers. 
• 3. Printing: The 3D printer begins to build the object layer by layer. It uses materials such as plastic, metal or even ceramic. These materials are often heated and then applied layer by layer until the entire object is finished. 
• 4. Finishing: After printing, the object can sometimes be worked on to give it a smoother surface or additional details.