CAT does indeed stand for Category. Beginner men start at CAT5 (also sometimes listed as "Citizens"). Beginning women may also race CAT5/Citizen with the men. Beginner Women's class starts at CAT 4 and you upgade(to 3, 2, 1 and Pro) by racking up points racing . More info can be found at usacycling.org.
Espoirs are young riders, under 23.
Hope this helps.
p.s. I'm lucky, I ended up in a tiny little town in IN that has a strong cycling community![]()