Complex sentence: "Craftsman Furniture" refers to the Arts and Crafts furniture of Gustav Stickley's Craftsman Workshops, popularly referred to as Mission Style Furniture, a term which Stickley despised.
Split into simpler sentences: Craftsman Furniture refers to the Arts and Crafts Movement style furniture of Gustav Stickley's' Craftsman Workshops. It was sometimes popularly referred to as Mission Style Furniture, a term which Stickley despised.