A professional reference is a recommendation from a person who can vouch for your qualifications for a job. Generally, you will be asked for 3-5 references by HR or the hiring manager after you have gone through the interview process. These individuals will be contacted to share feedback about working with you, either with a short survey or in a phone conversation. It is different than a letter of recommendation.
Letters of recommendation provide a detailed and persuasive argument for why and how the subject of the letter (you) should be admitted to the program you are applying for. Typically letters of recommendation are used as part of an application, most often for advanced degree programs but also for selective programs like fellowships, scholarships, or experiential learning.
If employers are asking for three professional references, you simply need to list their contact information.
