Terroir is a French concept
to describe the environmental factors that affect a crop's phenotype, including unique environment contexts, farming practices and a crop's specific growth habitat. Collectively, these contextual characteristics are said to have a character; terroir also refers to this character.
Terroir is the basis of the French wine appellation d'origine contrôlée (AOC) system identifies an agricultural product whose stages of production and processing are carried out in a defined geographical area – the terroir – and using recognized and traditional know-how. The specificity of an AOC product is determined by the combination of a physical and biological environment with established production techniques transmitted within a human community. Together, these give the product its distinctive qualities.
The defining technical and geographic factors are set forth in standards for each product, including wines, cheeses and meats. Other countries and the European Union have similar labeling systems. The European Union's protected designation of origin (PDO and PGI) system has harmonized the protection of all geographical indications and their registration. When labelling wine however, producers may still use recognized traditional terms like AOC, and are not required to display the PDO and PGI logos or terms, mostly for aesthetic purposes.
OK, long definition, but what it ultimately means is that there are certain foods that are specific to an area. It's tied into the concept of slow food, which promotes local foods and traditional gastronomy and food production. Conversely, this means an opposition to fast food and industrial food production. Something which is better for the environment, and definitely better than being vegan and having your quinoa flown in from South America.
But he's basically talking about how the term "terroir" can apply to other regions, which is the short form of what I said above.
Anyway, check out the slow food movement if you like your food by region and season.