Evolution in the broadest sense explains that what we see today is different from what existed in the past. Galaxies, stars, the solar system, and Earth have changed through time, and so has life on Earth.
Biological evolution concerns changes in living things during the history of life on Earth.
It explains that living things share common ancestors. Over time, biological processes such as natural selection give rise to new species. Science is practiced in many ways besides direct observation and experimentation. Much scientific discovery is done through indirect experimentation and observation in which inferences are made, and hypotheses generated from those inferences are tested. For instance, particle physicists cannot directly observe subatomic particles because the particles are too small.