Can somebody please Explain to me Natural Selection Thank You ;)

There are natural variations within a breeding population (not associated with mutations)...

Within the population there will be those who are a little faster, a little taller, etc...

If any of these natural variations give the bearer an advantage of survival in that particular environment those individuals will be more likely to survive and create offspring...

This differential reproduction will produce a genetic drift toward individuals better suited to that particular environment - they will be naturally selected...

As animals have offspring the offspring are slightly different from the parent. The difference may be a bigger beak or longer legs etc. The mutated animal does either better or worse than the parent animal because of their mutation. The animal with the better mutation generally survives and passes it's mutation on to it's offspring. And the new generation is a different species because it has a bigger beak or longer legs etc. Also know this takes place over thousands of years.