Where is your village? Who has it now?

If the invaders have policies like the Ottoman ones, such as "Iskan", a lot may change in your life:

In a few years, some folks from the invaders' own lands will be removed from their homes, and settled to your village to help with assimilation, stabilization and growth. These can be harmless nomads that the state wishes to put to work; or they might belong to a problematic and violent clan or family that your masters would rather have you deal with than their already productive villages in the heartland.

You now answer to a new lord, but the government is a lot more centralized; so you might have trouble getting used to the fact that your "lord" is a little more than a statesman. He does not own you or the property you work on; but a mere percentage of what is produced. Depending on the title he bears, he can be a noble aristocrat with little interest in what you do, someone with a military position in charge of working the land to help raise troops (the Timar system), or an Ayan/Agha, a wealthy guy with powerful connections and political ambition. The lord can even be a devshirme, a previously Christian kid from that neighbouring village that got conquered 40 years ago. Your elders probably recognize him.

Speaking of devshirme. You might be subjected to it, you might not. If it is decided that your village will participate in the program, someone will brief you. You will see some villagers sending their children away to keep them from being taken, and some will be volunteering their kids; because if they are talented, they won't be soldiers, they will be statesmen, they will be lords with their own villages. The devshirme system is a meritocratic one.

You however, are too old to fear that or have a shot at a better career. You need to figure out how to deal with the tax change first and foremost; because if you are a Christian, you will pay higher. Not too high, but your budget changes need to be adressed nonetheless. On top of that, your lord answers to a regional government, which is highly militarized and may have some quotas to fill, which in turn means you might have to work harder. Depends on your job.

You are not forced to learn the new language, change your religion or culture. However, you will see the merit in adapting; as you pay higher as a Christian, you can't communicate with anyone other than your lord's local lackeys, and you will eventually get tired of the conflict you might be experiencing with the village's new arrivals. Their culture is the state's; yours isn't. They are relatively safe, at least in that department; you aren't.

u/shamanicbro covered the case of the Ottoman Empire quite well, so on that score I'll refer you to his post.

 

Now, within Christian Europe? You likely wouldn't notice much of anything. The concept of a "country," did not really exist as such yet, and so there wasn't a whole lot for you to be attached to. Your political horizons were effectively the manor on which you worked, and generally neither the boundaries of the manor nor the terms of service would be altered significantly, simply because it was more convenient to maintain an already functioning manor in more or less the conditions the new owner found it. Likewise, the laws of a region were generally maintained as they were.

In fact, you might not even have a new owner. Having traded away the fief, the old overlord no longer has a claim on the fealty of the lord, and very often in these cases the lord of the manor simply swore fealty to their new overlord under more or less the same conditions they served previously.