In the first screenshot you can see more colors than just black and white. This makes for more contrast throughout the page. It makes the body pop and helps differentiate the headings for each other and the main section. The heading and paragraphs are in different fonts as well.
The two headings are found in the middle to show importance. Everything else is left aligned so it is easier to read and looks nicer.
The two headings are the same color and the authors name at the bottom is the same color as the headings. This gives the page a little bit of repetition.
The headings and main section have space in between to show they aren't the same. The paragraphs in the main section are closer together though, to show that they are part of the same section. This gives the page good proximity.
As these two pages show CARP can make a very big difference. I learned that in CSS you can hit the plus next to properties and add a lot of things as long as you know what to type.