While you may be thinking that a job interview is a job interview, interviewers may invite you for various kinds of meetings for different reasons.
In large companies, interviewing typically takes several stages. They are screening and selection. Each of the stages may have sub-stages and the higher the ranks of the position that you are applying for, the more sub-stages you are likely to go through. For example, if you are applying for a position of Senior Vice President of Human Resources with Fortune 1000 company, you may have 10-20 separate interviews with high-rank executives from the company.
The smaller the company, the more likely screening and selection are to be combined into one interview and performed by the same person, typically the president or the business owner.
The goal of a screening interview is to quickly sort out applicants and separate best qualified from the rest. A screening interview may sometimes last 5-10 minutes and may happen on the phone or using video conferencing. The reason why employers choose to use technology at this stage of the interviewing process is simple: they want to make sure that candidates have the necessary skills before they invest time into interviewing them in person.
A screening interview may also be held at the work site of the employer, career or job fair.
The person that conducts a screening interview typically works for the human resources department of the company. It may also be an independent recruiter. This person typically has no authority to make a hiring decision. The person who decides to hire you would usually be the department head or a high-ranked executive in a similar position.
The person that will be conducting a screening interview is likely to be more experienced with interviewing because he or she interviews more people than the executive does.