FDM stands for "Fused Deposition Modeling." It is a type of 3D printing technology that works by depositing layers of melted plastic filament to build up a 3D object.

Here's how it works:

1. The 3D model is sliced into thin layers.

2. The printer heats up a plastic filament and extrudes it through a small nozzle.

3. The nozzle moves around according to the design of the 3D model, depositing the melted plastic in the shape of each layer.

4. The layers are cooled and solidified, and the process is repeated for each successive layer until the object is complete.

FDM is a relatively low-cost and widely available 3D printing technology, making it popular for both personal and professional use. It is also relatively easy to use, as the printer follows a set of predetermined instructions to create the object. However, the resulting objects may not have the same level of detail or accuracy as those produced by more advanced 3D printing technologies.