I'm trying to understand what the following symbol is for. It's found in this schematic.
This device is a transient voltage suppressor for USB D+ and D- signals. It protects the device from static voltages that may develop when inserting or removing USB devices to connectors.
The four diodes (on side) act as clamping diodes that conduct to suppress ESD.
This or similar device can be found in this Semtech catalog
Looks like electrostatic discharge (ESD) protection on a USB port. Any port that a user can touch should have protection against finger zaps frying the chip connected to it.
Have a look at the datasheet for TI TPD2E001 to get an idea what the specs might be.