It's called resection, and it requires at least two known points.
It is possible, but in all honesty it requires having a relatively good idea or where you're located at already, and the ability to see those known points. It's reliable, if the other points are known, but it takes good terrain association skills and relating what you see to what's on a map, something most people don't have.
That being said, resection is accurate, if you are correct in identifying your landmarks. Otherwise you'll be completely incorrect and place yourself somewhere else entirely.
Also, don't forget about converting between your grid and magnetic declination That'll throw you off as well.
https://en.m.wikipedia.org/wiki/Position_resection