What is evolution?
Through out the years, a lot of things has changed including all organisms that lives in that moment. The changes including; their characteristics of a species over several generations in response to the environment, and that it happened gradually over time, or it's something that doesn't change in an instant, and that its the process of a natural selection in which it's a process that happens naturally to form a better traits that could easily adapt to a specific environmental pressures. Including the competition for food, mates, changes in climate, etc.
What is the different between Fact and Theory?
Fact and theory are often got merged together, even though there are quite a lot of significant differences between both. Facts can be identified as things that happens around us or truth that has been verified. For example, "It rains outside" while theory is a an explanation that include scientific methods that has been tested and confirmed.
How do species evolve?
Every species has their own DNA, and that occasionally DNA mutation or the changes of DNA will occur in the gene as it passes from generation to generation, which affected it's appearance, behavior as well as how the body works in general. The mutation could be a new version of that species and that it could help them to survive better in their environment which will make them likely to have more offspring.