Communicable diseases are caused by pathogens like bacteria or viruses and spread from person to person (e.g., typhoid, chickenpox, COVID-19). Non-communicable diseases (NCDs) are not contagious and result from lifestyle, genetics, or environment (e.g., diabetes, cancer, asthma), with the document highlighting their rise in India due to processed food and inactivity. Communicable diseases require hygiene and vaccines for prevention, while NCDs need lifestyle changes like diet and exercise.