A niche market is a focused, targetable portion of a broader market in which specialized products or services can be sold. Catering to the unique demands that aren't being addressed by mainstream providers, businesses pursue niche markets as a way to build loyalty and revenue with a largely-overlooked audience.
Rather than offering a general cleaning service, an entrepreneur might pursue a niche by offering exclusively floor polishing services. Another business in the same city might occupy a separate niche, specializing in the use of exclusively biodegradable cleaning products. Markets of any discernible size contain multiple subsets, although not all of the possible niche markets will be worth targeting.