From Investopedia – “Assets under management (AUM) is the total market value of the investments that a person or entity manages on behalf of clients. Assets under management definitions and formulas vary by company.”

You should be familiar with Grayscale by now, as they have brought Bitcoin and other crypto assets to the stock market for every day and institutional investors (GBTC, for example). They have now surpassed 5B AUM, an exceptionally high number in a short period of time. They have famously been buying more Bitcoin than is being mind, as there is clearly demand for it in their products. If you ever question whether institutional money is interested and invested in crypto, this is a clear sign that they are.