Wikipedia says: "A cottage industry is an industry—primarily manufacturing—which includes many producers, working from their homes, typically part time. The term originally referred to home workers who were engaged in a task such as sewing, lace-making or household manufacturing. Some industries which are usually operated from large centralized factories were cottage industries before the Industrial Revolution. Business operators would travel around, buying raw materials, delivering them to people who would work on them, and then collecting the finished goods to sell, or typically to ship to another market."
I believe the term is now commonly used to describe goods - any goods - that are still made by hand by a select group of people in a space that is not considered to be a storefront.