A niche can also be a demographic segment such as a particular income, location, etc.
Niche is basically, "find a hole and fill it", which is why all successful businesses are, in essence, niche businesses.
Be careful not to be too many things. It clouds the message and is difficult for the public to remember. My current business has one theme even though the offerings are vast. But the message and the niche market I want are clear. My retail store will have a much narrower product line, but the niche, the hole I fill, will be the same.