Micronations — sometimes also referred to as model countries and new country projects — are entities that pretend to be independent nations or states but which are unrecognized by world governments or major international organizations. These nations often exist only on paper, on the Internet, or in the minds of their creators. [Wikipedia]

[Principado de Sealand]

A microstate or ministate is a sovereign state having a very small population or very small land area, but usually both. Some examples include: Nauru, Singapore, Liechtenstein, Monaco, and Vatican City. [Wikipedia]