How do games like skyrim allow the meshes to be modified (in the characters face section for instance)?

One way I was thinking about doing it was to simply have shape keys (as they are called in blender), that I could then apply to the mesh with sliders, but 1. I don't know if such a file format exists or if I'll have to come up with a format myself, 2. I don't know if "shape keys" if the official name for what they are (basically they are hierarchical (or not) vertex modifiers), and 3. I don't know if this is the way to go, or if I'm complicating (or simplifying) things here.

Any insight on the subject would be much appreciated, and thank you in advance.

Ok thanks, morph targets seems to be the closest to what I was looking for search wise. I still don't know if there is a file type I should be using to store these targets, or if there is no convention regarding that. Should I just export the targets to a file and use it with the mesh it belongs to?