Espionage is obtaining protected information covertly. Counterespionage is detecting and defeating that activity. Counterintelligence is the broader effort to understand and neutralise the capabilities of those who would conduct it.
Espionage is the act of acquiring confidential or classified information without authorisation, through covert means. In a corporate setting this might be a competitor obtaining unreleased research, a planted device capturing boardroom discussion, or an insider passing information to an outside party.
Counterespionage is the active discipline of stopping espionage: detecting surveillance, identifying methods and actors, and removing the vulnerabilities that enabled them. It is operational and specific. A bug sweep, an insider threat investigation and a behavioural assessment of a sensitive role are all counterespionage activities.
Counterintelligence is broader and more strategic. It is the effort to understand, anticipate and degrade the information-gathering capabilities of an adversary, rather than to address a single instance. In the private sector the line blurs, and the practical work most organisations need sits under counterespionage.
Corporate, or industrial, espionage is simply espionage conducted for commercial advantage rather than national interest. The methods overlap heavily with state tradecraft, which is why the countermeasures are the same in kind. We cover this in detail on corporate espionage.
Naming the problem correctly points to the right response. A technical threat calls for TSCM; a human one calls for insider threat work; a behavioural one calls for behavioural intelligence. Most real situations involve more than one.