u know there are some character rare-used, for most of us we wont touch them for our whole life....lol..........in the chinese language, we have 正体字、异体字、俗体字. For the characters that we often use, they are called 正体字. 异体字 and 俗体字 come from the long chinese history. The traditional chinese has been kept using for about 2000 years. And it's complex. So for some unofficial cases, people simplified some very complex characters by themselves. These simplified characters formed the simplified chinese today and some unofficial characters which are called 异体字 or 俗体字.
The changes of this official file are almost nothing. It just says some 俗体字 becomes 正体字 or it uniforms the way we write 异体字 or 俗体字 ----- as i said, people simplified them by themselves. So one character may have more than one simplified way.
anyway, we dont need to care about what changes except you are a chinese language expert.