Definition
The term second interview refers to a meeting scheduled as a follow up to a screening interview. Companies oftentimes schedule multiple interviews with job seekers, narrowing the field of viable candidates after each round.
Explanation
Companies will oftentimes conduct multiple interviews; especially if the open position requires a complex skillset or plays a critical role in the organization's success. Initial (first) interviews are then used to screen candidates. Individuals that meet the basic requirements of the position will "pass" this initial screening process. These individuals are then invited back for a second interview.
The questions asked during the first interview likely assessed the candidate's ability to adapt to, and thrive in, the company's culture. In this second round, companies are more likely to utilize behavioral questions, which are meant to uncover the candidate's depth of knowledge and experience. These interviews can be conducted by one interviewee; however, it's more common for the candidate to face a panel.