Pantone home page <
http://pantone.com/pages/pantone/index.aspx>.
While Pantone is branching out to other areas such as textiles, they are most known for their "Pantone Matching System", or PMS (they no longer use that name).
Pantone sells ink to commercial printers, and also Formula Guide swatch books. For instance, a rather "John Deere-like" color is #355. The printer would mix 13 parts Pantone Green, 3 parts Pantone Yellow, and 1/4 part Pantone Black.
The swatch books are expensive, but worth it if you're doing any design work.
You can access the Pantone colors via the Photoshop color picker. In the upper right corner of the picker, click the "Color Libraries" button, and you'll see the vrious Pantone libraries, as well as some others. To go back to the regular picker, click th "Picker" button.