Ecology is the science of the biological relationships and interactions of the living beings with one another as well as with their environment. One can distinguish between autecology and synecology. An important concept is the ecosystem, the understanding of which requires a system approach.
In colloquial speech the word ecology is often used in the sense of "environmentalism", ecological in the allegoric sense of "clean, responsible towards the environment". So it is a common fashion to call oneself an ecologist without any schooling and without much understanding of ecological processes. If we like it or not, that's what it is.
(Me, to be an ecologist, I have studied three subjects at university and I've worked several years in agriculture. One cannot reach the same without an effort.)