dear Syed Farhan Hasany i think is *STL file, SLT stands for stereolithography, a popular 3D printing technology using in industry right now. if you using sofware cad/cam, have option to save in format *stl file
Dear Prof. Syed Farhan Hasany , I would like to extend the answer added by Mahmud Mahmud .
To 3D print an object, you first create a digital model using CAD software like CATIA or SOLIDWORKS. This model is then exported as an STL file, which represents the object's surface as a mesh of triangles. Next, you import the STL into slicing software such as Ultimaker Cura or Creality Slicer. Within the slicer, you configure crucial print settings: these include layer height, infill density, temperature, and print speed, tailored to your specific 3D printer. The slicing software then processes the STL and generates a G-code file, which contains the precise instructions for your 3D printer to build the object layer by layer. I hope, this is useful.
Both answers from Mahmud Mahmud and Vivek V. Bhandarkar are great. I just wanted to add something I wrote a while back about STL files and the format that may be of some use to you and others. Here is a link the explanation: https://www.hitechmex.org/titanium/stl/stlmarch17.htm
This “STL” was originally for a Titanium Bone Implant but should still be useful in this discussion.