Neutrophil extracellular traps (NETs) are fibrous structures released by neutrophils in response to stimuli, composed of chromatin, histones, and granule proteins. They play a dual role in host defense against pathogens and can cause tissue damage and inflammation. NETs are formed through two pathways: suicidal NETosis, involving NADPH oxidase (NOX), and vital NETosis, independent of NOX. NETs contain proteins with cytotoxic effects on pathogens and host cells. While beneficial in pathogen elimination, excessive NET formation can worsen inflammation and contribute to diseases like autoimmune disorders, atherosclerosis, and cancer. This review summarizes the composition and functions of NETs, highlighting their roles in host defense against invasive pathogens, autoimmune diseases, and cancer. NETs are categorized into suicidal, vital, and mitochondrial types, each with distinct formation mechanisms. The composition of NETs varies based on stimuli, and their components influence disease progression. NETs contribute to antimicrobial defense by trapping and killing bacteria, fungi, and viruses, but can also promote cancer progression and autoimmune responses. Understanding NETs' roles in disease is crucial for developing therapeutic strategies.Neutrophil extracellular traps (NETs) are fibrous structures released by neutrophils in response to stimuli, composed of chromatin, histones, and granule proteins. They play a dual role in host defense against pathogens and can cause tissue damage and inflammation. NETs are formed through two pathways: suicidal NETosis, involving NADPH oxidase (NOX), and vital NETosis, independent of NOX. NETs contain proteins with cytotoxic effects on pathogens and host cells. While beneficial in pathogen elimination, excessive NET formation can worsen inflammation and contribute to diseases like autoimmune disorders, atherosclerosis, and cancer. This review summarizes the composition and functions of NETs, highlighting their roles in host defense against invasive pathogens, autoimmune diseases, and cancer. NETs are categorized into suicidal, vital, and mitochondrial types, each with distinct formation mechanisms. The composition of NETs varies based on stimuli, and their components influence disease progression. NETs contribute to antimicrobial defense by trapping and killing bacteria, fungi, and viruses, but can also promote cancer progression and autoimmune responses. Understanding NETs' roles in disease is crucial for developing therapeutic strategies.