Synthetic assets are a system that allows users to create 24/7 financial markets related to any value.
For example, right now there does not exist a financial market future for the US Unemployment Report. If you wanted to trade against it, or include it in a portfolio that represents a snapshot of the US economy, you would be unable to.
But, with the BAO protocol, all you need is to have an oracle track the price and then you can create a synthetic asset that has a price related to US Unemployment.
Synthetic assets can track anything including the price of existing assets, allowing 24/7 worldwide access to markets.