What is allopatric and sympatric speciation?
Allopatric is when a species is separated by a geographical barrier and then speciate, Sympatric is when a species is separated by ecological or behavioural differences.
Allopatric speciation is like when a population of a species is separated by a mountain or ocean for a long enough time (around 3 million years) that they become different species, due to mutations and slowly differing gene pools, and can no longer interbreed to produce fertile offspring.
Sympatric speciation is when a population of species are separated by behavioural or ecological barriers. For example a species of finch may eat berries from a certain area filled with a type of bush and another population of that species may eat a different type of berry from another nearby area this seperation if it lasts long enough results in two different species that cannot interbreed to produce fertile offspring.
Sympatric Speciation also covers behavioural barriers such as different mating dances or calls these are rarer instances of speciation but also can cause two groups of the same species to speciate to become different species.
I hope I explained this clear enough for you.