Several communities comprising populations of various organisms (biotic components) that live together in an area and interact with non-living things (abiotic components) of the environment fomi an ecosystem. The communities in an ecosystem get everything that they need for their sustenance from the ecosystem itself.
Examples : A pond and a forest are natural ecosystems while an aquarium and a garden are artificial ecosystems (man-made).
An ecosystem consists of biotic components (plants, animals, microbes) and abiotic components (soil, air, water, minerals, light, etc) which interact with each other in a particular region.