tl;dr: current is what kills, but at least some voltage is required in order for it to go through your body.
For a better explanation from an actual electrical engineer, I recommend you to watch this ElectroBOOM video.
So, first of all, lots of people seem to not understand what actually kills you, and some even claim that mains voltage is “safe” because they have been shocked before and survived. Well, lemme break it down to you by firstly saying that, if you are one of those that survived and say that it’s safe, you were just lucky because, yes, you can die from an AC shock, be it 110V or 220V. What kills is the current, not the voltage.
The voltage, in layman’s terms, is just a way to get current through your skin, and usually anything over 60V is already capable to deliver current through your body. That’s why you can touch with dry hands both terminals of a car battery and not feel a thing (they are rated at 12V), since there isn’t enough voltage to make the energy go through your skin.
Current, on the other hand, is the actual amount of energy that’s running through a medium, and its unit of measurement is the Ampere (usually represented as A or amps). This is not 100% accurate, but should be enough for you to understand. A better and more didactic explanation of current and voltage can be seen here.
Now you may ask how many amps one needs to die. Well, anything over 100mA is already enough to kill you if it goes through you heart, since it could mess with your cardiac cycle, and then you’d probably discover what lies on the other side of life. You can see the effects of current through a human body on the chart on the left (taken from here). Anything over 1A should be enough to burn you to a crisp.
As for why those who say they survived a shock from mains voltage actually did it, it’s probably because current didn’t go through their hearts, it likely went through their right body side or only through their hands, in which case it will hurt a lot, or even burn you, but won’t kill.
A common thing that electricians do when dealing with high voltage is stuffing their left hands into their pockets, as so if they happen to get shocked, current won’t flow through their hearts.
If you ever plan to mess with wires in your house, turn off the breaker or be sure to be well insulated (rubber gloves/boots, for example) and you should be safe.
Also, don’t listen to the ones that tell you that you’re safe to mess with electricity with your bare hands because you aren’t touching ground. Ceramic and concrete, even though they do have a somewhat high resistance (concrete absorbs and holds water; you can also look for Ufer ground), do serve as grounding for electricity, since mains voltage is high enough to go through that resistance.