In the UK, a person e.g. a student, who has some short-term work experience without being employed permanently is undertaking a "placement" or an "internship". If you want a job and the employer wants to check you have the practical skills to do it, you may be required to undertake a "work trial". This is common for chefs where it is obvious within minutes or hours if you can do what you say you can do.

most call it an internship. If you are studying nursing in a hospital you are interning for a career as a a nurse.