Micronationalism is the founding and establishing, and, after that, running, of a micronation. A micronation is an state-like entity unrecognized by any macronations (states recognized by the wider international community, i. e. the United States, Germany, Rwanda, Australia, etc.), but run similarly.
Micronationalists are split between two mindsets: Secessionism and simulationism.
Secessionist micronationalists (secessionists for short) wish their micronations to some day secede from their host macronations and become recognized and politically
independent states. Micronational secessionism is thus a non-violent political movement.
The definiton agreed on by several micronationalists is "[a] micronation [...] which peaceably anticipates and plans for, through legislative drafting and infrastructural development, eventual
macronational [...] recognition."
Simulationist micronationalists (simulationists for short) do not have the goal of seceding from their host macronations. They run their micronations purely as a hobby and may deviate somewhat from the normal makings of a state, for instance having stuffed animals as citizens.
Some simulationists also claim to be a political movement.
And then there are those in between. They do not actively attempt to gain political independence and recognition from macronations, but would grab the chance of becoming independent.
Some simulationists take micronationalism to the point where it turns into the creation of a fictional universe ("conworlding"). Some other micronations, the Usian Republic among these, do not recognize the conworlding micronations.