Each step will first have an English description. Some of the descriptions will have formulas to help explain exactly what it is doing. For example, in the image above, the first step shown says "Factor difference of two squares." It then has the formula for factoring two squares, which is a^2-b^2=(a-b)(a+b). The next line after the description is the expression that the step started with. The items highlighted in green are what the step is changing. The next line is the resulting expression for the step. The changes from the original expression are in blue.
Most steps will have the green and blue highlights for what is changing. However, not all of them will. Some steps may just have a description with the resulting expression.