“Plus sizing” has varying definitions, but essentially when it comes to apparel, plus size means anything beyond the standard XS-XL size range. Plus sizes may range from 1X to 3X, or 1X to 6X.
Sometimes called extended sizes, plus sizes usually cover sizes 18 and up. In the U.S., the general cutoff for plus sizing is size 14 and over. It also varies by brand, however — many U.S. brands won’t make anything beyond a size 12 or 14.
Inclusive sizing is another term outdoor brands are using more and more. Inclusive sizing refers not just to plus sizes, but a wider range of sizes for every body type, including short, long, petite, tall, maternity, and plus sizes (for all genders).