The term full-stack developer is somewhat controversial in the tech community, while many dispute the existence of such a nomenclature, many do. Full stack comes from the English of "full stack" or better "all layers", then first we need to understand that this term has adapted its meaning. I remember when I started working with technology over 10 years ago, many used this definition for people who understood all layers of web development, including frontend, backend and infrastructure/database. Currently, when someone refers to a full stack, he is probably referring to a developer who works in two layers: Frontend and Backend.
There is a joke to refer to a full stack developer as the duck developer. Because the duck swims, walks and flies, but does not do any right. I think it's possible for a developer to be good at everything he does, but for sure the vast majority who call themselves full stack aren't. If you look at my blog or even my linkedin, you will see that I use the term full stack, although I don't like it very much, it's more because the term is used by people and recruiters when they find you. At the end of the article I'll talk a little more about why I don't think this term is the ideal one to use today.
Pato Developer Controversy