What is a real spy and what is the difference between a spy and an agent? Please give me an example.

It’s the same! It’s just a different name!

Spies in a broad sense:

Spies refer to agents who are secretly dispatched by spy intelligence agencies to the target country (region) to engage in various illegal espionage activities, mainly stealing secrets. Refers to national citizens who are secretly recruited by the other party's spy and intelligence agencies to serve them. Broadly speaking, a spy is a person who engages in covert detective work, spying on confidential information from an enemy or competitor or performing sabotage activities to benefit the party he or she works for. Also known as agents and secret agents.

One of the main tasks of spies is to steal information through illegal or legal means, secretly or openly, and also carry out covert acts such as subversion, assassination, kidnapping, explosions, psychological warfare, and sabotage. A person who is sent or paid to spy on secrets, intelligence or carry out sabotage activities.