There are 2 file types use the .TEX file extension:
1. LaTeX Source Document
A TEX file is a source document prepared by LaTeX, a high-quality typesetting system. It may include text, symbols, mathematical expressions, and graphics. TEX files are commonly used in computer science, electrical engineering, statistics, economics, and physics for typesetting articles, books, and other publications.
You can open TEX files with various LaTeX applications, such as TeXworks (multiplatform), MiKTeX (multiplatform), and Texmaker (multiplatform).
Since TEX files are saved in plain text, you can also open and edit the files with a plain text editor, such as Microsoft Notepad (bundled with Windows) or Apple TextEdit (bundled with macOS). However, these text editors do not provide helpful LaTeX syntax highlighting features provided by LaTeX applications.
Updated: December 16, 2020
2. Texture File
Bitmap image used for storing textures; can create the appearance of different surfaces and can be applied to both 2D and 3D objects; often used in video games (such as first person shooters) that support 3D texture-mapping.
Example video games that use TEX files include Avalon Heroes (which actually uses the .DDS format for its TEX files), Serious Sam, and Dead Rising 2. To open the TEX files used by Dead Rising 2, first rename them to have the ".big" extension, and then open them with Gibbed's DeadRising2 Tools.
TEX files can be opened by some programs that reference textures or use texture-mapping. They may possibly be opened with a generic image editor.
Updated: May 25, 2012