An ecosystem is a system in a space with its living beings, their interrelations and their relations with their surrounding consisting for example of geology, soil, climate, also human influences. To understand all the interactions, a system approach is necessary.
The factors of the inanimate nature include the climatic conditions (the ecozone, the height, the microclimate), the geological ones, the pedological ones (soil structure, minerals and pH of the soil, water capacity, cationaic exchange capacity ...).
A forest, the sea, a bog, an ivy-covered house wall are examples of ecosystems. And after all the biosphere is the biggest ecosystem.
The togetherness of all the living beings of an ecosystems is called a biocoenosis.