What does full figured mean?  It represents a body type.  It is relevant to fashion because when selecting a garment, size matters.

Dictionary.com (March 2019) "Full figured is having an amply proportioned or heavy body."

Plus size is interchangeable with full-figured.  A relatively new alternative term for plus size (or large size) gaining consumer and editorial favor is curvy. In a euphemistic sense, curvy is regarded as less offensive to those that wear larger sized clothes.  Plus size clothing is clothing proportioned specifically for people whose bodies are larger than the average person's.

Full figured is essentially having a plump or curvaceous body.  Full figure or plus size fashion comes in a wide variety of styles, fabrics, and sizes.

Lane Bryant began trading in the early 1900s as a producer of clothing for "Expectant Mothers and Newborn"'. By the early 1920s, Lane Bryant started selling clothing under the category 'For the Stout Women', which ranged between a 38–56 inch bustline.  The earliest catalogs used illustrations to sell their products, but by the mid-1950s photographs were integrated into the catalogs as the evolution of printing technology made this option available. After a hiatus through the 1960–1980 period, Lane Bryant again began using plus-size models.

Fashion designers are starting to look more closely at the earning potential from plus-size clothing, and have used plus-size models for their advertising campaigns and catwalks.

You may also have interest in Plus Size Fashion or Plus Size Clothing Stores.