Level A - beginner-intermediate & intermediateYou have been taking lindy hop classes for around a year or more. You know the basics of Charleston, Lindy 6-count, Lindy 8-count, Swing out and its basic variations, can lead/ follow it at parties.
Level B - intermediate-advanced & advancedYou are rocking the Lindy hop parties in Prague on regular basis, you take classes but also participate in workshop. More difficult Lindy hop variations are a piece of cake for you, you can lead/follow them fluently. You can dance to slow and fast tempo. You've been doing this whole fun for some time already. (About 2-4 years.)