The G-spot can be very difficult to find on a woman, but the general spot for it is on the front wall.
It's 2 to 3 inches inside & on the top. It's a bump that kind of has a walnut shell texture. To stimulate it during intercourse, try an obtuse angle. If the girl lies on her back & raises her hips up & the guy leans back a little onto a pillow or something, the penis will be angled upward when it enters the vaginal canal & stimulate the G-spot.
if she's on her back, it's inside about 2-3 inchs on the bottom, feels wrinkly,, for the love of god trim and smooth your nails if you're looking for it or she won't be happy.
Deep in and slightly to the front if the vagina. You know when you hit it. Trust me.
Assuming you are speaking of yourself and you're a female,...
The elusive G-spot is located on the back side of the pubic bone. Insert your index or middle finger into your vagina, follow the contours of your vagina in and up, feeling the back side of your pubic bone. The G-spot is a more solid mass of flesh that has a texture to it that feels like the surface of a walnut.
Now, what it does for you and how, that's different for every woman
After you have her wet through playing with her clitoris and have inserted your entire finger, you will feel it as you press up towards her pelvis/stomach.
They vary in size and exact position but usually go quite firm. Some girls like them gently pressed and massaged, some like your finger to go back and forth almost flicking it. She will tell you what she likes.
Oh believe me, you will know. It is different on every girl so it takes some adventure to find it sometimes.