Coronary artery calcification (CAC) represents a clear sign of advanced atherosclerosis and a strong indicator of coronary artery disease burden and cardiovascular risk. Beyond its established prognostic value, CAC significantly influences plaque biology, lesion morphology, and the technical complexity of percutaneous coronary intervention (PCI). This review summarizes current knowledge on the mechanisms of vascular calcification, its clinical determinants, diagnostic assessment, and therapeutic implications. Vascular calcification is now understood as an active, regulated process involving osteogenic transdifferentiation of vascular smooth muscle cells, inflammatory signaling pathways, extracellular vesicle release, and disturbances in mineral metabolism. Distinct calcification phenotypes exert different effects on plaque stability: micro- and spotty calcifications are frequently linked to plaque vulnerability, whereas dense, sheet-like calcification is more typical of stable fibrocalcific lesions. The prevalence of CAC increases with age and differs between sexes, while cardiometabolic risk factors, chronic kidney disease, systemic inflammation, and genetic predisposition further contribute to its development. Noninvasive computed tomography remains the cornerstone for CAC detection and quantification, enabling reliable cardiovascular risk stratification. Intravascular imaging techniques, particularly intravascular ultrasound and optical coherence tomography, provide detailed characterization of calcified plaque morphology and support optimal procedural planning. In patients with heavily calcified lesions, intravascular imaging-guided lesion preparation and stent optimization represent the most effective strategy for improving PCI outcomes.