These headings are statutory classes, not screening scores. Choosing a class only sets context for reading published FAA material. Standards live in Part 67. Decisions live with an AME and the FAA.
14 CFR Part 67 Subpart B
First-class
Airline transport context
First-class standards are the strictest vision, hearing, and cardiovascular monitoring rules of the three classes. A published CACI still has to be read against first-class items.
Second-class is the usual context for commercial privileges. Published pathways are not ranked by class in this tool; class notes appear on the result when they exist.
BasicMed is a separate statute. Some conditions that required a special issuance still constrain BasicMed. This tool does not determine BasicMed eligibility.