In population ecology, density-dependent processes occur when population growth rates are regulated by the density of a population.
For example: for dioecious (separate sexes) obligatory parasites, mated female worms are required to complete a transmission cycle. At low parasite densities, the probability of a female worm encountering a male worm and forming a mating pair can become so low that reproduction is restricted due to single sex infections. At higher parasite densities, the probability of mating pairs forming and successful reproduction increases.
Negative density-dependence, or density-dependent restriction, describes a situation in which population growth is curtailed by crowding, predators and competition.
There also exists density-independent inhibition, where other factors such as weather or environmental conditions and disturbances may affect a population's carrying capacity.
An example of a density-dependent variable is crowding and competition.
So density independant means that factors such as weather and other enviromental factors affect population growth while density dependent means that over- (or under-) crowding, predators, and competion affect growth of a species.