It's Application which installing contents like textures / maps to garry's mod.
Link to bin (for windows): http://adf.ly/1Urm3m
- Download setup from link and install
- Select content which you want to install
- Press Download / Install and wait
- If you will see "[Ready to install]" like "Counter Strike Source [Ready to install]" select it again ang press Download / Install button.
- Enjoy