A density-dependent factor affects a population size positively or negatively because of the size of that population. Examples of this are predators hunting more of a specific prey in an area due to increase in population or food supply of a species declining due to rapid growth of a population.
A density-independent factor affects a population no matter the size. Human activity, such as deforestation affects many populations. Also, natural distasters and tropical storms are examples of density-independent limiting factors.