The size of the text for that tag. A size of 8px is small and 48px is very large. Our body text is 14px. Some examples of the sizes are:
This is the font weight. Checking this box makes the text "bold" as compared to "normal" weight.
This is the color of the page itself it can be a solid color or an image. Usually if we are using an image we also use a background color that is similar so when the page loads and the image hasn't loaded yet there isn't a huge difference when the image does load. For example if the background color is black and the image is white it would be hard on the eyes to instantly go from dark to light.
Are you using tables?
If your page setup uses tables check this box so the text in them will be controlled too, we use the same options as the body text. If you aren't sure check it anyway if your page has no tables it won't hurt.