In those with male anatomy, this usually means removing the foreskin. This may be done for medical reasons – e.g. a foreskin that is too tight – although this is rarely needed and it is more frequently for cultural or religious reasons. This is very common for those of the Jewish faith and more widely in North America, for example, although less so elsewhere.
There is significant debate over whether this is right or wrong in cases where it is not medically necessary. Many people feel that putting a baby or child through this pain unnecessarily and permanently modifying their body is cruel or abusive and some argue that it should be banned.
In the context of female genitalia, the meaning usually relates to a far greater act of abuse, often referred to as Female Genital Mutilation or FGM.
Although thankfully rare in the western world, there are still many places where this is practiced and barbaric injuries are inflicted on girls and young women. More information on this is available from the World Health Organisation.