I don't know how many times that you have to be told that the web site you are looking at are wrong before you understand. Web sites can be wrong it happens, kind of like how priests can molest children they shouldn't but it happens.
Evolution is the theory of how from the first replicating organism diversified and evolved. I always recommend the good people at Berkeley to explain evolution in a correct and easy to understand way. Here is their web site and the definition of evolution from their web site. Stop using the web site you have and use Berkeley one they have the entire theory correct on their site.
Understanding Evolution
"Biological evolution, simply put, is
descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations). Evolution helps us to understand the history of life."
For the Big bang I suggest you read the article from the University of Michigan they have a very good article that explains it very well. It even points out a few holes in the theory(oh my). Here is the web site and a highlight from the site.
THE BIG BANG
About 15 billion years ago a tremendous explosion started the expansion of the universe. This explosion is known as the Big Bang. At the point of this event all of the matter and energy of space was
contained at one point. What exisisted prior to this event is completely unknown and is a matter of pure speculation.
If you want to question theories good for you, science is about questioning theories but you should at least understand the existing theories and the evidence behind it. Otherwise you are wasting your time and appear to be uneducated.