The Tier 5 Youth Mobility Scheme (YMS) allows citizens of Australia, New Zealand, Canada, Hong Kong, Taiwan, the Republic of Korea, Monaco, and Japan (you need to be sponsored if you're from Taiwan, Hong Kong or the Republic of Korea) to work and live in the UK for two years.
The Tier 5 visa allows you to work in most jobs, except playing or coaching a professional sport or working as a doctor in training. Once in the UK, you cannot extend the YMS unless you return home to apply for entry clearance through a different visa.
Applicants must be 18 to 30 (if you turn 31 while you’re in the UK, you can stay for as long as your visa is valid), must have £1890 in their bank account and may not bring any dependents with them.
For more information see gov.uk