When people mention an “X file,” they usually mean a file ending in the `.x` extension, the part after the final dot such as in `model.x`, where the dot helps signal the file type to systems like Windows or macOS in the same way `.pdf` or `.zip` hint at their formats, though this naming is only a convention since anyone can rename a file and different software may reuse the same extension for unrelated formats.

Since a `.x` file can mean a DirectX model format or a Lex lexer file, the easiest identification step is to check the workflow it came from and then inspect it in a text editor, watching for DirectX indicators such as `xof 0303txt` with mesh structures, frames, and numeric lists, or for Lex-like syntax showing `%%` sections or `%{ … %}` code areas.

If the file shows garbled characters in Notepad, it might be a binary form, but you can still look for readable clues like `Mesh` if it’s DirectX-related or token-style text if it’s Lex-based, and it also helps to turn on real extension visibility in Windows (File Explorer → View → “File name extensions”) because what looks like `something.x` could actually be `something.x.txt` or even `something.x.exe`, altering how the file should be handled.

A single extension like `.x` ends up with multiple meanings because file extensions are informal conventions, not globally governed identifiers, which means any group can adopt the same suffix—letting `.x` serve DirectX model formats in 3D pipelines while also representing lexer source files in development tools—something that happens frequently with short extensions whose limited pool encourages collisions.

Another reason is that an extension often represents a loose category of formats rather than one strict standard, and some formats even come in multiple encodings such as text or binary, so you can encounter very different-looking `.x` files within the same ecosystem; meanwhile, Windows relies on simple file associations instead of deeply analyzing contents, meaning the same `.x` file might open in a 3D tool on one machine and a text editor on another, and because extensions are easy to rename—on purpose or by accident—you can also end up with files whose true contents don’t match the label at all.

Because of all that, the surest approach to interpreting a `.x` file is to use the surrounding project together with a quick text-editor check for familiar headers or patterns, and if you share the initial 10–20 lines or note the software source, I can determine which `.x` type applies.

The reason `.x` varies in meaning is that extensions are informal conventions, letting completely unrelated communities choose the same short suffix for entirely different kinds of files, and since operating systems mostly rely on user or system-set associations instead of content detection, a `.x` file may open in a 3D program on one machine but load in a text editor elsewhere, making it appear as though `.x` has multiple definitions.

Some `.x` formats offer multiple modes, like text versus binary, so two files in the same `.x` family might appear totally unrelated when opened in Notepad, and with extensions being so easy to rename, mismatches between label and content happen often—so using context and inspecting the first lines is the safest way to identify the real `.x` type.