Look at the descriptions you find online describing gifted / highly gifted / profoundly gifted children.
If you are not experiencing anything extraordinary, then that is great too - it is just not a gifted or HG / PG profile.
It is genetic. You already would have an inkling that it runs in your family trees.
The years from 0-preschool are most amazing. 1. The gifted person does not remember those years, so when they witness it in their own child, it is astounding, shocking and unnerving.
2. It blows parents away because it shows that we are born this way and knowledge is very healthy and natural. For example, not everyone needs to be taught how to read. Some people teach themselves by age two years for example.
Due to the internet, people are sharing and accumulating their experiences, normally these people are dispersed. We are finding common experiences and abilities.
Every ten points of IQ probably does make a difference and you can see it when you study a larger population of high IQ people.
Mensa might say that every 1 out of 50 people can be gifted, but gifted people probably wish that were the case. It might be the case on the campus of Stanford University for example.
A non-gifted person would not be happy in a highly gifted environment. You'll be able to tell right away. The gifted people are true brains. Some people think baseball pitchers do amazing things. This is very similar but you can't really see what's happening because it is inside someone's mind, but it is amazing nonetheless - not physical per se, but mental achievement - not movie star hype, just old-fashioned genius, maybe along the lines of Edison, Franklin, Socrates, Plato, anyone that is known for true mental genius. You know it when you experience it. There's an energy to it. It's intense.