As its name would seemingly imply, the Chestburster stage of the Xenomorph life cycle results in the small, snake-like version of the nearly unkillable alien creature violently breaking out of the victim’s chest cavity — pretty much destroying the torso in the process.
Once the Facehugger has implanted the baby Xenomorph into the host, there isn’t much that can be done to prevent the final birth.
This process is pretty much the same across all organisms who find themselves unfortunate enough to host a Xenomorph, and the process almost always leads to immediate death for the owner of the aforementioned chest.