A QROPS is a Qualifying Recognised Pension Scheme, commonly used by expats living in countries such as Switzerland, Denmark, Sweden, the Netherlands, and France. It allows you to pick up your pensions from the UK and transfer them into another jurisdiction.
Prior to 2006, anyone who left the UK would leave their pensions behind. Basically, this pension would be dormant, as they would no longer being any contributions being made, and would remain dormant until the member reached their retirement age, usually 65. So the individual would still have to follow UK pension rules even if they have since left the UK.
This all changed in 2006 with the introduction of QROPS, which is an approved HRMC scheme.