Nothing, they are different names for the same investment vehicle. They are also sometimes known as listed managed funds, exchange quoted managed funds (EQMFs) or quoted managed funds.
An Active ETF is a managed fund traded on a stock exchange. They function like managed funds, but traded like shares which can be bought and sold during trading day on the stock exchange. Active ETFs are actively managed by fund managers to generate alpha and outperform relevant benchmarks.
Active ETFs will aim to beat the benchmark using a number of active investing strategies. They operate in a similar way to traditional managed funds but have the benefit of transparent, live intra-day pricing and market making ability which ensures liquidity
Investors invest in the Active ETF by using a stockbroker as if they were buying a share. Similarly, liquidating the investment follows a similar process to selling a share. This means that your Active ETF can be monitored and reported like any of your other shares.