Every USB device, whether it is a charger, fan, or USB stick, can be equipped with a chip on which payloads (scripts) are loaded. Even a charging cable. Once plugged into your notebook, PC or phone, these scripts run automatically and can cause malware, keyboard logging or even destruction of your notebook by electric shock. The latter is extreme, but the tests are online. Data can also be copied from, for example, your telephone in this way.
Now it all sounds serious but it is an awareness month. These things happen and are very lucrative for individuals who want to break into companies, the loot is often large. Imagine that as a cybercriminal you rent a room in an expensive business hotel. You can then quietly open the existing USB connection, add your chip and everything works again as it should. However, every phone that is vulnerable to this will fall victim to, for example, malware and this can be an entrance to the company where this person works again.
Tip: For companies: turn off USB for your employees by default. If you find a USB stick, report this to the IT department, maybe more have been found (and an attack is underway). Throwing it away is also a good option, don't let it win your curiosity, because the criminals play on that.
If you are on the road in a hotel, take a power bank with you and charge as much as possible via an adapter. Optionally, adapters are available (USB data blocker) that only allow current to pass and no data so that you can safely use the USB ports for charging.