Which term refers to the act of spying to obtain confidential information?

The term that refers to the act of spying to obtain confidential information is espionage. Espionage involves various methods of gathering secret information, typically involving secretive and clandestine operations. This can include not only the theft of documents but also electronic surveillance, infiltration, and other techniques to acquire classified or sensitive data from governments, organizations, or individuals.

Understanding espionage is crucial within the broader context of national security and intelligence practices because it highlights the threats posed by foreign and domestic adversaries seeking to undermine a nation's security or competitive advantage. The study of espionage also informs counterintelligence efforts, which aim to detect and prevent such activities by adversaries.