Here's a breakdown:

* Everywhere on Earth with life: From the deepest ocean trenches to the highest mountain peaks, evolution is happening constantly in every ecosystem.

* Within populations: Evolution doesn't happen to individuals, but to populations over time. This means changes in the frequency of genes within a population.

* Across generations: Evolution happens through the gradual accumulation of changes in gene frequencies over multiple generations.

* Driven by natural selection: The driving force behind evolution is natural selection, where organisms with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits on to their offspring.

Therefore, evolution is an ongoing process that happens continuously in every place on Earth where there is life. It's not a single event or a specific location, but rather a constant change within populations of living organisms.