STL is a file format commonly used in 3D modeling and 3D printing. It represents a 3D object using a series of connected triangles to create a three-dimensional surface. The format is widely supported by most CAD software and 3D printing slicer programs. STL files are essential for creating physical objects through additive manufacturing, as they provide the necessary information for the 3D printer to generate the object layer-by-layer. When designing a 3D model for printing, it is crucial to ensure that the STL file is well-structured and error-free to avoid print failures and inaccuracies. Understanding the basics of STL files is vital for anyone involved in 3D modeling and 3D printing, as it serves as the bridge between digital designs and physical objects.