Breadth: Being broad in scope. Carrying items in many different product categories. Offering several different types of service under one roof.
This means that you try to offer everything a customer might want, even if it’s only remotely related to your product or service offering. If you are a remodeling company you might do everything from adding a closet, to trimming out some cabinetry, to building a patio, up to a complete kitchen remodel.
Depth: Being intense in scope by immersing your business into an industry or product category. Stocking a focused product mix, a specialized service offering.
One example is a landscaping company that does only irrigation systems, or only commercial work. The key word being only.