What is the difference between realised and fundamental niche?

Realised and fundamental niche are two different environmental conditions in which species exist in an ecosystem. The fundamental niche is the range of environmental conditions in which a species is technically capable of living (certain conditions for food, temperature, shelter, etc.). Whereas the realised niche is the range of environmental conditions (space) where the species actually lives. The realised niche is a result of different species pressuring and threatening each other into separate and narrower niches due to predation and limited resources. For example the fundamental niche of the Grauer’s gorilla is the majority of the eastern Congo rainforest. However, due to predation, deforestation, war, and poaching the realised niche of the Grouer’s gorilla is the forest of the Albertine Rift in eastern Democratic Republic of Congo. Therefore, the realised niche can be said to be a subset of the fundamental niche.