Much of real property law in this country is common law originating in England and dating back hundreds of years. You have to understand that in order to grasp the two concepts with which we will be dealing here.
Up until very recently in history, really only the last couple of centuries, the vast majority of people in the world tilled the soil. Even so, there was famine, with people starving to death. In fact, famine in Europe was one of the causes for colonization in the New World.
Since it was vital that the land brought forth its highest yield, the common law theory was that the person farming the land ought to be rewarded. Consequently, whenever someone openly continuously, notoriously, hostilely and exclusively possessed and improved land for a period of ten years he may have become the owner of that property, even if the record owner had been paying a mortgage and/or the taxes on the property. Ownership under these circumstances was acquired by adverse possession. Use of the land of one party by another party for a specific purpose (for instance, walking over someone√Ęs land as a shortcut to your own), openly, continuously, notoriously, hostilely and exclusively for a period of ten years could have created an easement by prescription.
This is still the law today. Consequently, when your neighbor has put up a fence that is encroaching one foot on your property, after ten years the property could very well become his. Or if your neighbor has been going back and forth over your property an easement could have been created which means that you cannot later stop your neighbor from trespassing your property.
What, you ask, does all this mean? It means that it is very important to have a survey when you purchase real property and to make sure that all the property that you are supposed to be getting will be yours.