A g-spot short for Gräfenberg spot, known to be an area inside the vagina when stimulated leading to a strong orgasm. A g-spot in reality is just a spot inside the vagina that stimulate the internal parts of the clitoris through the vaginal wall which then leads to pleasure. Not everyone with a vulva has a g-spot.
In the case of people with a penis, the g-spot is the prostate and can be stimulated inside the rectum.
People experience pleasure differently and it is important to communicate and explore with your partner to understand what they prefer or what gives them pleasure. Masturbation is a great way to know your body to know what works for you.
Sources:
https://www.healthline.com/health/g-spot-in-women#What-is-the-G-spot?