It's really good, you could make sandwiches out of it! I don't think it has to be pork, you could probably make it out of any kind of meat if you wanted to. The texture is light and fluffy, but the flavour is very intense because of the soy sauce and how dry it is - so it's got really good contrast.
I think it's an asian thing, so if you've lived in urban California or Hawaii you've probably come across it some time in your life.