GTK (GIMP Toolkit) is a library used by many GUI apps (Wireshark, Chromium, VS Code, etc.) to render windows, buttons, and menus.
The gtk-2.0/gtkfilechooser.ini file configures the file picker dialog — the window that appears when you click "Open File" or "Save As" in any GTK-based app.
nvim language extensions
Terminal emulator
terminal file explorer