Exactly like that, but different.

A hybrid adopts a different set of characteristics than a gravel bike.

Hybrid: road-ish frame (hardtail, hard fork), slightly wider tires, flat handlebar, mtn bike gearing
Gravel: road-ish frame, significantly wider tires (but still not fat bike), drop bars, mtn bike or road bike gearing

In the Trek lineup, the list the Domane under both the road bikes and gravel bikes; it's basically a road bike with slightly wider tires.

Both hybrid and gravel are a "crossbreed" of road bike and basically a mountain bike, but different characteristics are passed.