You have just reached the interview stage of the job application process and are now expecting to meet your prospective employer not face-to-face, but through a telephonic interview.
These days, many companies and recruiters use phone interviews as the initial screening technique to pare down the number of candidates for any job opening. These interviews save cost and time for the company and are especially useful when an employer is considering out-of-town candidates. Whatever be the reason, at any point in your job searching process, you could be asked for a 20-30 minute phone interview. Like a face-to-face interview, you need to be prepared for a phone interview too.