An internship is a form of work experience. Internships are most commonly done in universities, businesses, and non-profit organizations to give students or young people the opportunity to learn new skills while gaining valuable experience.
An intern can be paid for their services by the organization they are working with but usually receives no remuneration in return. Some internships have minimum hours required where an intern must work for a set number of hours each week. Interns may be unpaid interns or paid interns and can sometimes also be called “trainees”. A trainee is typically employed as an apprentice or trainee before being promoted to full-time employment. The definition varies between jurisdictions (e.g., some countries use “intern” while others use “apprentice”).
Internships may also last from several weeks up to one year depending on the organization, industry, job role, and time commitment required by the employer/employee relationship.
In many cases, employers prefer hiring recent graduates because they perceive them as more likely to provide added value than experienced professionals who might already have several years of relevant work experience under their belt. However, there are numerous other reasons why employers might hire recent graduates over older workers including:

An intern is a person who works in an internship to gain more experience or broaden their horizons etc