Employers will usually interview the most qualified candidates for a job. If you are requested to attend an in-person interview it usually means that the employer is making a final decision from a small number of candidates. It is also possible that a telephone interview will be conducted in addition to an in-person interview.
Job interviews usually last for about 30 minutes. The employer asks a series of questions to help them determine the suitability of each candidate. This is the candidates opportunity to expand on the information they provided in their resume and to highlight how their particular experience and skills make them the most suitable candidate.