To keep a stable balance of our Earth nature tries to put limits on all of us so we don't over-crowd ourselves. These 'limits' are labeled as Limiting Factors defined as things that keep populations from growing any larger. Limiting factors are the environments include: Food and water, oxygen, space availability, as well as other factors such as predation and competition.
Now there are 2 types of limiting factors density-dependent and density-independent factors. Density-dependent factors are competition, predation, parasitism, and disease. Competition is when organisms must compete for life-sustaining things like when two animals fight for a water supply in a desert. Predation or when one animal hunts another for food, it is one of the best known methods of regulating a population and consists of a predator-prey relationship an example is when a wolf hunts a deer. Now parasitism, it is when a parasite lives in another organism and feeds off of its host and consequently harms it, an example is a flea or tick living and feeding off a dog's blood. Disease is a quite harmful one that even puts a limit on even us humans, it is a disorder from the way organisms naturally function an example is when a human gets a cold and can't function or think as well as it could if the human was not sick.
Now, Density-independent factors are quite different from density-dependent factors, the independent factors are mostly what we can't try to keep control of such as weather. Unusual weather is a density-independent factor that we can't control much like when desert gets unusual amounts of rain or temperatures are low instead of high. Natural disasters like hurricanes, tsunamis, and earthquakes are another thing we can't control are one of those independent factors. Seasonal cycles like our seasons are another one that affects us. Even certain human activities such as damming a river or clearing a forest for farm land are a factor.