Why are there two Irelands? What are they called independently?

Ireland is an island in the United Kingdom. The famous partition of Ireland in 1921, under the Government of Ireland Act 1920, made it into two distinct jurisdictions, Northern Ireland and Southern Ireland. Northern Ireland is still a part of the United Kingdom as a Sovereign state also named Ireland. The southern part became the Irish Free State, called as the Republic of Ireland.

This is the reason why there are two Irelands.