Expedition resurrection items allow you to bring your Explorer back to life after they are defeated, so you can continue the same expedition instead of ending the run.

Each revival continues the same expedition. Nothing resets, and all progress stays intact. 
You can revive multiple times in one expedition as long as you have enough resources.

The important thing to understand is that the cost increases every time you revive within the same expedition.

Example:

The first revival costs 1 resurrection item. The second revival costs 2 resurrection items. The third revival costs 3 resurrection items...and so on, and this keeps increasing in the same way for every additional resurrection you make.

This means longer expeditions can quickly become expensive if your Explorer keeps reaching zero health points, so it’s worth using resurrections strategically rather than automatically.