"Pollination" is really a type of formal definition referring to the process of delivering a male gametophyte (pollen grain) to the female gamete (egg). Formally, pollination is the transfer of a pollen grain from an anther to a stigma (in flowering plants -- the angiosperms) or to the area of the ovule in more primitive, non-flowering plants (the gymnosperms, such as ferns).

"Fertilization" refers (usually) to the actual fusion of the male gamete with the female gamete.

I bet you can figure out your second question on your own, just be breaking it down into its parts. External refers to "outside the body" and you already know what "fertilization" refers to. So... "external fertilization" means that the gametes (sperm and egg) are released externally and the fusion to form the new embryo occurs externally (outside of the mother's body). This often is referred to as a "spawn." Most marine invertebrates use this method as well, as do many freshwater species of animals. Contrast this with "internal fertilization," which is the method used by most mammals. Think about the different "challenges" that external fertilization/spawning poses as compared to internal fertilization. For example, an external fertilizing situation poses problems with dilution (how does the sperm find the egg?) and with avoiding being eaten by other animals while an internal fertilizer has different challenges. Can you think of "strategies" used by the animals that help overcome these challenges?