What is an ecological system?

I believe that this question is asking about Urie Bronfenbrenner's ecological systems theory. In his model, the ecological system is the environment that a child grows up in. That environment, which is made up of smaller environments, or systems, interacting with each other, affects and shapes that child's development.
The overall environmental system is divided into four subsystems or levels. The first system is the microsystem. This is the system that a child has the most direct contact and interaction with. It would include teachers, peers, siblings, parents, and so on. An example of how this system affects the child's development is that when a parent reads a bedtime story to the child, the child's language development is improved. Self-esteem can be improved by surrounding the child with encouraging friends.
The next system is the mesosystem. This one could look a lot like a food web because it involves all of the interactions that exist between components of the microsystem. Parent-teacher conferences or emails between teachers and parents are good examples of this. Both systems are involved with the care and development of the child, but they are involved in different ways; however, their combined efforts can greatly impact a child's development socially, mentally, and emotionally.
The third system is the exosystem. This system involves the connections that exist between a child and a setting that affects the child; however, the child has no (or almost no) contact with this system. A parent's place of work would be a part of this system. The school district and curriculum review boards would also count. Changes that are made to an entire school curriculum obviously will affect student learning and child development. A parent's stressful job or sudden loss of a job could affect the child as well. For example, if a family's income is suddenly cut in half, that child might not have as many social interactions as before, or physical development could even be affected if less food is being provided.
The final system is the macrosystem. This system involves cultural factors or even national factors. For example, poverty-stricken countries are likely to have fewer educational opportunities for children, and physical development may be hampered because of malnutrition.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.471.7361&rep=rep1&type=pdf