The word carat comes from the Carob Mediterranean tree whose seed was used for centuries as the standard of weighing precious gems. Each carob seed weighs approximately one-fifth of a gram. A carat is one-fifth of a gram.
Jewelry & Diamond Industry Dictionary of Terminology
An artisan or person that creates, repairs, or modifies jewelry.
Bench Jewelers generally follow the apprenticeship model, from Apprentice to Journeyman to Master, with varying degrees and areas of focus within each level. The term "bench jeweler" varies from "jeweler" a jeweler may focus on a single or few skillsets whereas a bench jeweler tends to have a larger knowledge base and skillset due to their work environments and responsibilities. A Jeweler may do a single task for their employment, such as stonesetting of specific sizes and types of gemstones, often in a manufacturing type environment. A Bench Jeweler more often is employed by smaller organizations and has a wider range of responsibilities.
Most Master Bench Jewelers utilize numerous skillsets throughout their career, to include silversmithing, goldsmithing, platinumsmithing, laser welding, stonesetting, fabrication, forging, wax carving, 3D design software, 3D printing, lost-wax casting, electroplating, and finishing or polishing.
Sources for these definitions are GIA.edu, Google.com, Meriam-Webster.com, and Wikipedia.org.