The simple fact of the matter is that we know a vast amount of information about people who sexually abuse children. What will follow is just the tip of the iceberg, and I will only cover four categories: General information, motivations, preferential abusers, and non-preferential abusers.
Please understand that entire books have been written about motivations and the various typologies of sexual abusers, and that this information is only designed to give general information about each category, not necessarily specific factoids.
We know that most abusers are heterosexual, male, and adult, although a small minority of abusers are gay, lesbian, transgender, or pedophilic and less than 5% of abusers are female. 35.6% of abusers are juveniles when they commit their offense. Abusers come from all religious backgrounds, but are generally more likely to be religious than not. There is no profile for those who sexually abuse children.
Some abusers are pedophilic, or preferential abusers: They have an ongoing sexual attraction to children, and this factored into their abusing a child in some way. While it is true that most abusers are non-preferential, around a third are.
There are healthy ways to manage a sexual attraction to children without hurting children, and most with this attraction do not become preferential abusers. It would be helpful if those with a sexual attraction to children knew they had options for support and treatment and that they are not destined to abuse children, and it would be helpful to have more research on this population to reduce stigma and fill in our knowledge gaps.
Some preferential abusers remark that they wish they knew that help was available to them before they abused a child, and it is available, but not widely known. Part of the purpose of this site is to shed light on what support options are available before abuse can occur.
Motivations vary greatly. Some abusers are incestuous, and that is one area that needs more research compared to other types of abuse and motivations. Some abusers seek power over someone, and the child happened to be an available way to do that. Some abusers have unmet psychological needs, and the child was an available outlet. A very small percentage of abusers are motivated by the sexual pleasure they get from children, and an even smaller percentage get pleasure from knowingly causing children pain. Some abusers have antisocial personality disorder and lack the empathy needed to prevent their behavior. Juveniles who sexually abuse have motivations that are likewise diverse, though it should be noted that most victims do not go on to sexually abuse others. It should also be noted that people do not wake up and decide to sexually abuse a child: Weeks and months are typically spent grooming the child, breaking down their own barriers that might prevent them from abusing a child, and coming to a situation or planned interaction that will lead to the abuse.
Non-preferential abusers, or abusers who are not sexually attracted to children, make up most abusers, approximately 60-70%. There are a wide range of typologies and motivations, which is partially addressed by the information available here. However, the wide array of information available can be a distracting rabbit hole that is better left for researchers, law enforcement, and other professionals.