Answer: The statement implies that the hackers psychologically manipulate the human to access the information they need.
Explanation: The author states that the hacker does not only exploits technology to get system access or to gather information. But there is another pivotal part of hacking. He refers to this part as "social engineering".
Social engineering from information security perspective means manipulate human emotions and convincing them to disclose some confidential information. Hacker often hacks or defrauds after gaining confidence and trust of a person.
Phishing is an example. It is a fraudulent technique for getting some secret information. Phisher sends an email pretending to be from some reputable organization to persuade people to divulge private information like passwords and credit card numbers, ATM card pin etc.