Can someone explain the clock sync?

Regardless of how it works you will never know it's an improvement until you stop using the clock and compare. It may be a PITA but it's the only way to really know.

@jastralfu I know how to do it, I have it set up. What I wanted to know is what it does. How does it work? Thanks.

@jond I just want to know what exactly it does.

I am talking about the 2 BNC Cables connected to the clock output of the DAC to the clock inputs on the Hermes, what does this accomplish?

It should sync the Hermes internal clock with the Terminator clock as the master.  It is intended to reduce jitter.

I would not worry about any of the clock stuff. The whole jitter-worry is overhyped as with anything remotely contemporary, jitter is not audible at the values found in contemporary digital devices. See here for a discussion:

https://audioxpress.com/article/audio-electronics-is-digital-jitter-really-a-problem

You don't worry about MHz output in the audio signal, as it is equally irrelevant. If you hear differences in DACs, it may be a whole lot of things before I would consider jitter.
Also the video linked above explains nothing about what is supposed to happen with this clock stuff, just how to do settings on a particular device.

Just enjoy the music!

@fthompson251 

This information from the Denafrips site should help

In short, your DDC reclocks the signal from your streamer before sending it down to the DAC. There’s also DSP that takes place. The objective is to lower jitter to levels where it is no longet a factor for the DAC. The i2s into the DAC is then extremely clean. This supposed to result in better sound.