Pink wine happily spans the colorspace between red and white wine, in a way, rosé is more like a state of mind.
Rosé happens when the skins of red grapes touch wine for only a short time. Where some red wines ferment for weeks at a time on red grape skins, rosé wines are stained red for just a few hours.
The winemaker has complete control over the color of the wine and removes the red grape skins (the source of the red pigment) when the wine reaches the perfect color.
As you can imagine, nearly any red wine grape (from Cabernet Sauvignon to Syrah) can be used to make rosé wine, however there are several common styles and grapes that are preferred for rosé.