Paul summed it up - don't get hung up on the categories.

That said, the Touring Kayak category vs. sea kayak is a group of kayaks that have hatches and bulkheads or just one bulkhead. They are usually one notch up from the recreational boats that have no bulkheads or hatches. "Touring" meaning to carry some stuff and go a bit longer than a few hours that the rec boat usually does. The Sea kayak usually gets a bit more official with better construction, a bit longer for more speed, usually rudders or skegs and more attention to details and a higher price tag.

http://www.wildernesssystems.com/product_category/index/products/touring/