When designing 3D models and 3D printing, you're likely to encounter a variety of file types. Some file types are related to the design software, some are associated with 3D scanners, and other file types are proprietary to certain brands of printers.
With so many different files, keeping track of what files are used for what processes can be confusing.
While there are many different file types that can be used in 3D printing and modeling, here's a list of some common file extensions you'll see in 3D printing:
OBJ: OBJ is an open file format that represents 3D geometry. It is a common file used in 3D printing because many design software exports to OBJ and most printers accept OBJ as a printable file.
STL: STL files are a standard file type that interfaces between Computer Aided Design (CAD) software and 3D printers. Most CAD software exports to an STL file and most 3D printers accept STL files.
VRML: VRML (or WRL) files are commonly used when a 3D model has color and you want to transfer that color to the print.
X3G: X3G is the file type that interfaces with the MakerBot 3D printer. MakerWare and ReplicatorG will output an X3G file.
PLY: PLY files are normally scanner-generated models that will have to be imported into some type of design software before sending to a 3D printer to print.
FBX: FBX is a file format owned by Autodesk. It is used to efficiently exchange data between Autodesk program including 3ds Max, AutoCAD, and Maya.