An "intern" is a student who does a job temporarily in order to learn more about a job or industry. The temporary job that they have is called an "internship".

Internships can be paid or unpaid. They usually last from one to six months. Most interns are college or university students, but sometimes people who are not in school can also do an internship.

Here's an example of how to talk about an intern:

What's our new intern's name?

Another concept that's similar to an "intern" but a little different is an "apprentice". An apprentice is someone who's learning how to do a complicated job by working alongside someone with a lot of experience. But an "apprenticeship" lasts longer than an "internship": years instead of months. Internships are more common for corporate office jobs, while apprenticeships are more common for jobs like electricians, plumbers, mechanics, and so on.