some animals have multiple offspring , like fish and turtles , in hopes that at least some of them will survive. These organisms that have large amount of offspring usually dont give extensive or any care in raising the offspring. They just hope that at least a couple survive to pass on their genes.
Organisms that only have a few offspring (ei monkeys, birds, humans, mammals in general) usually devote a large amount of care into raising their offspring. Most often the mother and the father raise the offspring, and the offspring has a very high chance of survival.
Both of these mechanisms are just to ensure the passing of genes.
Hope that helped XD