Citizenship simply means membership in a given country.
Citizenship is the virtue or quality of belonging to a state/country.
Citizenship is that status or legal position enjoyed by nationals of a country which entitles them to enjoy certain legal rights and privileges and at the same time, owe certain obligations to the country to which they belong.
A citizen could also mean a national. Note that not every inhabitant in a state is a citizen. In the state, there are people who are not legally recognized as members and such people are called Aliens. They are foreigners who have no right to citizenship.