A probationary period can be used to assess a worker’s suitability for the job. It’s not a separate period of employment and so a probationary worker should receive the same pay and entitlements as someone who isn’t on probation.
Work experience is the term usually given to a work placement associated with a young person’s education. Many high school students will undertake unpaid work experience as part of their school curriculum. TAFE and university students also do work placements as part of their course, and these are typically not required to be paid. Most other forms of work experience are no different to trial work.
Unpaid work trials should only occur if it’s necessary to evaluate a worker's suitability for a job. They should only consist of the worker demonstrating their skills relevant to the job’s required tasks or observation of others performing the work.
Unless it is part of an education or vocational placement, anyone undertaking any form of work experience or trial work that would normally be undertaken by a paid worker and that is of direct benefit to the business should be paid the legal minimum pay rate for that type of work.