A job interview on the phone is often is a first interview or the meeting could be a screening by a recruiter, to determine if your application will move to next step of the interview process. Meaning, they will or will not invite you to an in-person interview, which is naturally the next step. This is a way for an employer to filter out unqualified job applicants.
A phone meeting is a good sign that they liked what they saw on your resume and are interested in learning more about your qualifications. The phone interview is just as important as a face-to-face interview.