Fracture-related infection (FRI) ranges from uncomplicated infections in healed fractures to infected bone defects that require complex treatments and can lead to prolonged disability. The lack of a clear definition of FRI until 2018 hampered its diagnosis and study, affecting the quality of care. FRI affects mostly the lower limb, its incidence ranging from under 3% for closed fractures to over 30% for severe open tibia fractures. Risk factors include high-energy trauma and soft tissue injury, polytrauma, and relevant patient-related factors. FRI is mainly caused by pyogenic bacteria, with Staphylococcus aureus being the most common germ, followed by coagulase-negative staphylococci, enterobacteria, and others (in about a fourth of the cases, the infection is polymicrobial). These bacteria invade bone canaliculi and form biofilm on necrotic tissue and implants, complicating treatment, as systemic antibiotics are less effective against biofilm-protected microorganisms. This leads to inflammation, bone loss, and increased antibiotic resistance. Accurate classification of FRI is crucial for risk stratification, better-informed decisions, data comparability between studies and ultimately, improvement of patient care, but so far, no classification has been uniformly accepted. The latest classification considers three critical elements that determine prognosis and guide treatment: Fracture (F), Related patient factors (R), and Impairment of soft tissues (I).