Fraunces is a display, "Old Style" soft-serif typeface inspired by the mannerisms of early 20th century typefaces such as Windsor, Souvenir, and the Cooper Series.
The Fraunces font family is composed of a Roman and Italic, and is being built as a Variable Font. Between these two styles, the family spans 3 axes: Optical Size, Weight, and Goofy.
The optical size axis ties together changes in contrast, x-height, spacing, and character widths. As the optical size decreases, the x-height increases, spacing opens up, and the characters expand slightly in the width.
Many of the peculiar, wonky characteristics that are suitable for display usage are less desirable for more continuous reading. At certain smaller optical sizes (18px and less), specific characters are substituted for a more normalized character.
In the Roman, the characters that substitute are the h, n, m, and s. In the italic, the b, h, and v are swapped for a more simplified form.
The weight axis spans Light to Black. Nuff said.
The Goofy axis gives access to the chocolate-y, chunky forms that are available towards the Optical Min, but still retaining other Optical Sizing considerations, such as change in x-height, spacing, width, and subbing of more unusual characters.