Hemophilia is a genetic disorder where the patient has a deficient amount of coagulation factor (usually clotting factor IIX) in the blood - leading to trouble responding to blood vessel injury, internal or external. People with this diagnosis do not bleed more intensely than the normal person, but their body does not maintain fibrin formations (like a scab) allowing the blood vessels to heal in a timely fashion. Think of a patient on warfarin/heparin. Since the recessive gene presents in the X chromosome, females with the gene almost never show symptoms but are simply carriers of the allele - almost 100% of hemophiliacs are male. The disease is maintained with regular injections of the clotting factor, physical therapy to strengthen joints and lifestyle modifications (ex: no contact sports). Historically, hemophiliacs didn’t live past childhood but now life expectancy is estimated at 10 years less than the average male.
Hemophilia was once called the Royal Disease - the funny thing about genetic disorders is that they seem to crop up when you marry distant and not-so-distant family members. Most notably Alexei Nikolaeyich, the would-be heir to the last Russian Czar (and Anastasia’s brother), was a hemophiliac. Supposedly Rasputin (who would later betray the royal family) gained the Czar’s trust and confidence by using alternative medicine to treat the boy - as opposed to mystified doctors who prescribed aspirin (which obviously would not help to form blood clots).