a position particularly well suited to the person who occupies it
"he found his niche in the academic world"
(ecology) the status of an organism within its environment and community (affecting its survival as a species)
"The invasive plant's success was due to filling a niche where no native species could survive."
A cavity, hollow, or recess, generally within the thickness of a wall, for a statue, bust, or other erect ornament. Hence, any similar position, literal or figurative.
"The architect designed a decorative niche in the stone wall to house the marble bust of the founder."
In plain English: A niche is a special place where something fits perfectly and has its own unique spot to exist.
"Every business tries to find its own unique niche in the market."
Usage: As a noun, "niche" refers specifically to a small recess in a wall designed to hold an object like a statue or plant. In modern usage, it describes a specialized segment of the market that appeals to a particular group with distinct needs.
To place in a niche.
"The carpenter carefully placed the small statue inside a recessed space on the wall."
Pertaining to or intended for a market niche; having specific appeal.
"The boutique bookstore found success by catering to a niche audience of rare map collectors."
In plain English: When something is niche, it means it's very specific and only appeals to a small group of people who really care about that particular thing.
"The small shop has found its niche in selling rare vintage books."
The word niche comes directly from the French verb meaning "to make a nest." It entered English with this original sense, eventually coming to refer specifically to a small recess or specialized place for something.