In an energy pyramid, which level will generally have the LARGEST number of organisms?

The answer to your question:

Habitat is a set of the place of environmental conditions in which particular organism lives and adapt the situation accordingly. A niche is nothing but an idea or role played by organisms that how they can live in an environment including their diet, shelter, etc. Mainly niche is concerned with the factor of gaining energy by organisms and supplying it to other, in the ecosystem.