What does the statement "extinction and speciation are both parts of evolution" mean?

Extinction refers to the death of species with no further generation. It does not happen in a few years but gradually after few hundred or thousand years, a species become extinct. Similarly, speciation is the formation of new and distinct species in the course of time. Few species extinct and few evolve gradually.

Basically, these both are parts of evolution, because evolution is defined as the process in which living organisms develop and diversify from earlier forms during the history of the earth.