There are many definitions of niche. Simply put, it is a collection of life elements such as food, habits and habitats of a species. Encyclopedia has definitions, such as the position occupied by a population in the ecosystem in time and space and the functional relationship and role with related populations, but there should be more than one definition. Intraspecific competition leads to the widening of the niche of this species, and the stronger the competition, the greater the possibility of niche widening; Interspecies competition leads to niche separation, or a species is eliminated. There are only two situations in theory, but they are not. If the niches of two species overlap, but the resources are very rich, then the two species can coexist. There are pictures in many books, such as General Ecology of Higher Education, which I can't get. A brief introduction should be easier to understand, but there are still many things if the landlord studies them in depth, such as four-dimensional, five-dimensional and multi-dimensional minority images. I learned it from a competition, so please forgive my mistake.