There are a few reasons for why there are specific attributes to genealogy that I've discovered that I don't really see talked about.
Geography: Everyone has a birthplace and most ancestors have a place where they got married, or passed away. Ideally, when searching for ancestors or relatives, if you can find a city (maybe your grandfather's birth place) and work through locations around it, you are more likely to find more than if you solely focus on just that one city. For those in the U.S, many people have immigrated throughout the southeast, because of history and people have different lifestyle desires. Many of my ancestors in particular are in Southern Poland, or Central Phillippines.
Mathematically: There are many dates in geanology, estimates, and precisions. You're able to eliminate a lot of error potential if you have quantitative statistics. If you have a grandmother born in 1945, you could immediately construct that her parents were born X amount of years prior and either around the same year or long after. (In cases where the biological father dies while the mother is pregnant, or the mother dies in childbirth).
Biologically: This leads me to my next point of biology, for obvious reasons genetics is the science behind genealogy, you are related to certain people by blood through your genetics passed down to your parents, this helps us understand how exactly we are related to our family. Parents, grandparents, uncles, cousins, etc, it's all relation through biology and genetics. For example, my aunt Krystyna Przywarska is my 1st cousin 1x removed since she's my father's father's brother's daughter.
Faithfully: Sometimes you can't know for certain, sometimes you just need to trust that you're in the right direction. Any small piece of information helps, even if it's not entirely accurate. For instance, my paternal grandmother Helena once thought that her grandmother Magdalena Sodo's maiden name was Dąbek, after some research I actually was able to determine that it was actually "Wątek".
Finding graves is also a hobby of mine, along with something I feel very inspired about. As somebody who has family abroad and is unable to visit cemeteries, finding them online has been a tremendous help and I do occassionally like taking time out of my day to help people find theres! There are many websites for finding graves, but one primary one I use the most when networking is findagrave.