A level 1 commoner is, for instance, a teenager (or racial equivalent) either helping his Pa on the farm or just taking over the farm (probably a bit too early). He's the farmhand, blacksmith's apprentice, stablehand, baker's assistant, destitute street urchin, novice wheelwright, cooper (barrelmaker), or table-waiter.
A level 7 commoner is the experienced old farmer who's tended and protected his crops well into middle or old age, maybe even venerable age if he's particularly lazy and slow-working (or relatively untalented). He's fought off coyotes/wolves/stray dogs/street urchins who tried stealing some of his crops or eating his sheep/chickens/cattle/pigs. He's mixed it up in his fair share of bar-room brawls over the years, and survived probably more than one rough mugging where he had to struggle to keep the muggers from killing or crippling him. He might've joined the militia for a year but only for the free food or something, he probably didn't pay much attention and never had any real battles during the stint. Maybe he went to the village's defense back when that goblin tribe came by to make trouble, and gutted a few goblins with his trusty old farming sickle or his carving knife. He's struggled to save his crops from the occasional drought or flood, crop-blight or high-taxation period, hungry moles or rats or whatnot, and perhaps even an occasional wildfire or whatnot.
7th-level commoners might also be younger men or women who are just very talented at their trade, and have worked hard through adversity and hardship to be successful farmers/smiths/coopers/tailors/whatever. They may not be good at much, but they have a knack for their profession and they're very dedicated to making the most of it. They might've turned a rugged frontier field into productive cropsoil, fighting tooth and nail to ward off wild animals, bandits, amoral frontiersmen, and a greedy landbaron who taxes far too much for frontier acreage. It might be because they're enterprising or prideful, but it's just as likely or moreso that they had no choice and simply did what was necessary to make a living, regardless of the obstacles, because it was either that or die. They might not have what it takes to be a ranger or rogue or fighter, but they've got spirit and at least one significant talent. They're rugged by necessity and overcoming hardships, even though it all may seem pathetic to the likes of adventurers what with their risk-our-lives-daily-but-never-really-work-ourselves-bloody routine.
Etc.
The difference between a fighter and a warrior is that fighters get more formal training, and from better sources, and fighters are more dedicated as well as more talented. They practice harder and more often. They get real battle experience more frequently. They may spar a lot. The fighter devotes themselves to mastering various combat techniques, whereas the warrior just learns how to hit things until they die or give up, though the warrior may actually bother to spend a little time here and there learning an actual technique. The warrior spends less time in battle and trains less, practicing even less still, and relaxing much more often, or does menial tasks that let their combat skills degrade rather than putting them to the test. Warriors don't test their prowess as frequently against such difficult opponents or odds. They're probably more lazy and more cowardly, or they're militiamen who only practice occasionally in combat skills alongside working their farm or their smithy. Or they're just undisciplined and untalented. Warriors probably don't eat as well or exercise as well as fighters do, so their physique is likely to be less optimal. The warrior might be nothing more than a common street thug working a protection racket or serving the thieves' guild, or going around mugging folks, or partaking of highway banditry or pirating at sea, fighting only when necessary to secure the goods before making their escape.
