What is speciation? What are two processes that can cause it?

Speciation is simply the creation of new species.

Peripatric speciation occurs when a natural barrier (such as a mountain range, canyon, wide river, etc) prevent the original species from coming into contact with one another. Like you'll have one half of this original species on one side of the barrier and you'll have the other half on the other side. Eventually, over time, species on both sides will continue to mate ONLY with the individuals on the same side of the barrier as themselves and genetics plus differences in environmental pressures for adaptation eventually make it so that the original species becomes diverged into two.

Sympatric speciation, however, occurs when species diverge despite occupying the same geographical region.