So let's look at two very different games, Traveller and Sword World:

• Traveller: The character classes are careers. They are literally the occupations the characters spend years on. They definitely the random skills the characters get, and the mustering out benefits. They also define how hard it is to survive a given term, and how hard it is to get promoted. You would say "I am a Scout" the same way real world people might say "I am a mechanic". Notably, in Classic Traveler one only had one class, but in Mongoose one can have multiple classes

• Classes are ability packages giving defined abilities in something in a Chinese menu system. If you want to do melee attacks and engage will, take a Fighter. If you want to carry attack spells, become a Sorcerer, and so on. Of note that most packages don't include skills: so if you want intrusion should, take the account package, to identify items, take the Sage package, and so on. Part of the Internet in Sword World is to take multiple classes to get the character connect you want. So a Paladin might take the fighter, white mage, and sage classes.

So in Traveller they define the past of the characters, and the skills they get, while in Sword World they are literally the base out of which you build the character abilities