Internal and External Fertilization

Internal fertilization is characterized by sperm fertilizing the egg within the female; the three methods include: oviparity (egg laid outside female body), ovoviparity (egg held within female), and viviparity (development within female followed by live birth).

External fertilization is characterized by the release of both sperm and eggs into an external environment; sperm will fertilize the egg outside of the organism, as seen in spawning.

Internal fertilization can occur anywhere, it is not limited to a water habitat. Also, it allows to protect the organism from anything, and it is not just out in the open. A disadvantage is that the number of offspring is limited.
External fertilization does not provide protection from any predator to the organism. Many never reach the zygote stage, and if they do they have a chance at being eaten by predators. But, this form of fertilization produces a larger amount compared to internal fertilization.