Well, it depends on how strictly you're using the word "peasant." Historians tend to use it in the strict sense, which is roughly equivalent to a sharecropper -- someone who owns or rents a piece of land and owes a certain part of the harvest from it to their local feudal overlord. In that case you do whatever tending the crops requires of you (and as those of you MMM-ers who farm will know, that can be a huge range of things!) But often non-historians just mean anybody not noble, which includes -- well, all the things that people with recognizable English surnames would suggest: carpenters, cobblers, smiths, stewards, millers, bakers, brewers, shepherds, drovers, hunters, tanners, chapmen (traders), weavers, tailors. Lots of people who mostly worked the land had side-gigs for the off-season, and lots of them kept a few pigs or goats or cows. If you made your rent the lord mostly left you alone and let you do whatever you wanted. But... medieval life was anything but uniform and homogeneous -- the rules in one village might be completely different from the next village over. Tradition counted for a lot. In general if your great-grandfather got to graze his cattle for free on the village green, you got to as well, and so would your great-grandson. So in some ways social and economic life was less precarious than it is now. But also, really changing your status and your wealth was pretty damn hard. You pretty much expected to have your parents' life, for good or for bad.