Things that surround us including living or nonliving things makes the Environment. It includes physical, chemical and other natural forces. Living things live in their environment. They constantly interact with it and adapt themselves to conditions in their environment. All organisms (from virus to man) are obligatorily dependent on the environment for food, energy, water, oxygen, shelter and for other needs.
The relationship and interaction between organism and environment are highly complex. No organism can live alone without interacting with other organisms. So each organism has other organisms as a part of its environment. Each and everything with which we interact or which we need for our sustenance forms our environment.