In micronationalism, activity generally refers to a state in which a micronation or intermicronational organisation is actively and presently doing things: making laws, holding meetings, implementing policy and appointing officials. A micronation or intermicronational organisation that is not doing these things can be said to be inactive.
Given the transient nature of micronationalism and how consequently many countries can simply cease doing things while still formally existing, "inactive" is a useful colloquial term to use as a descriptor when a micronation has not legally ceased to exist, in that no paperwork has been published officially dissolving the nation or ceding its land claims, but has practically stopped operating in any meaningful way.
Whether a nation or organisation is "active" is a nebulous concept to define, but one useful indicator, at least for those polities that identify with the MicroWiki Sector, is that the MicroWiki page for the polity has not been updated in a significant amount of time, such that the contents have become considerably outdated.
It is unclear what characteristics of nations or organisations cause them to remain active longer. Elections have been anecdotally known to help generate activity, but there is no formal literature on the subject.
Intermicronational organisations tend not to remain active in the long term.