To me they are both the same haha
I’d have to agree with above, from my point of view cyclecross are race bikes that can ride on grass no problem while gravel bikes are more for longer rides and more relaxed. Plus gravel bikes are a little more mountain bikey then a cycle cross bike would be.
Great question! I actually use my CX bike for gravel!
Typically, a CX bike is short and snappier because it has to make sharp turns and steep climbs. For an actual CX race, the widest tire you can use is a 33. Think short, fast, and punchy! A typical gravel bike, though, is going to be more like a Cadillac than a sports car. It's longer and more forgiving, so it is more stable on descents. On the other hand, it makes wider turns. Gravel bikes can usually take wider tires, so you have much more comfort and stability.
I haven't really found a good carbon gravel bike that fits me (I'm pretty short). So when we're not in CX season, I put a set of 40s on my CX bike, with a wider cassette, and by necessity, a longer chain. The tires give it better stability, although it's still not as stable as a longer, more traditional gravel bike. But it serves my purpose since there isn't anything too crazy where I live.
That being said, I'm always on the lookout for a smaller gravel bike. Someday I will find one! Hope this helps. :-)