Still not 100% sure about what SEO is? This quick video from Common Craft is a good introduction.
Of course, your chances of ranking highly for a general search phrase like Pinot Noir are low. But you probably want to rank highly for searches that associate your winery (e.g. Kosta Browne Pinot Noir) and/or region (e.g. Russian River Pinot Noir) with a particular varietal.
Another example: V. Sattui recognizes that they are a popular picnic spot, and has optimized their site for searches relating to winery picnic.
If you don't know the top 3-5 search terms that bring visitors to your winery, talk to your Webmaster. Then take a look for yourself at where your site appears in the results when you type those phrases into Google. If you're not happy with the outcome, it's time to tackle SEO for your winery website.