Ecology, as you may have already guessed, is a science closely related to biology, psychology, and chemistry. Ecology focuses on the relationships between individual living things, like humans, and the chemical elements within their environment. You could call it a holistic approach to understanding nature.
Given the breadth and scope of ecology, though, it's often necessary to break it down into smaller categories that focus on different aspects of this relationship. For example there is population ecology, which studies the distribution of animals and plants; community ecology, which studies the ways in which communities of living things are organized and relate to one another; and paleoecology, which studies the ecology of fossils.