When dressing for an interview, you want to put forth a professional image and show the potential employer that you’re serious about becoming a member of their team. You can’t accomplish either of these goals when dressed inappropriately. So it’s important to put some thought into what you wear when dressing for an interview.
For a typical white collar office job, you want to wear formal business attire to an interview unless the person setting up the interview tells you otherwise. In the latter case, feel free to ask for clarification if you’re told something vague like “you don’t have to wear a suit” or if they say you can dress business casual. There’s nothing wrong with you confirming that you both share the same meaning of business casual.