Ecology is the study of the interactions between organisms and the environment. There are various scales of study in ecology, the largest being at the level of the ecosystem, the next being at the level of the community and the smallest is at the population level.
Sometimes when studying Biology, things like photosynthesis and respiration we always focus on what's going on inside of one organism but there's a whole branch of Biology that's says okay we get how one organism works but how is that one organism work with everything else? And that branch of Biology is called ecology, eco is a root word that means home. So this is the study of our home, how do we and the other organisms in this planet, yeah they're there too, how do organisms interact with each other and their environment? Now this can be broken down into things like how do organisms interact with each other? For example what's the prey of a particular predator? What eats what? What parasitizes what? If you have a tape worm, you're starting to get into this kind of interactions and I hope you don't.
There's also the study of how organisms interact with the non-living factors in their environment. For example people who did not understand this started cutting down deforesting things like the rain forest and now they're discovering that change the climate. If you get rid of rain forest, those rain forests are actually contributing to the lot of rain that's helping the farm land near the rain forest. Without the rain forest your farms start lowering their food production and you wind up cutting out more rain forest to get more farm land it's a bad thing. So it's really important that we understand this stuff, there's also a fair amount of stuff going into how do these non-living parts interact with each other? For example if you don't understand the water cycle it's hard to understand why you'll have different interactions. For example the water cycle is part of what's going on here with the deforestation process.
And understanding how currents in the oceans change in response to changes in heat for example out of the earth understanding that will help us understand how it's going to impact us. That's ecology, it's the study of us.