Ulster Scots, also known as Ullans, is the name given to the varieties of the Scots Language spoken in Northern Ireland and is recognised as such by the British Government in the European Charter for Regional and Minority languages and by the Irish Government in the Good Friday Agreement. Scots is spoken in parts of the region of Ireland traditionally called Ulster. Some enthusiastic individuals like to think of Ulster Scots as an independent language closely related to the dialects of Lowland Scots, hence the spelling using a hyphen: Ulster-Scots. This is linguistically tenuous. Scots is the member of the Germanic language family most closely related to English.
In the same way that use of Irish Gaelic in Northern Ireland is sometimes a political sign of the faction that desires all of Ireland to be united and sovereign, use of Scots in Ulster is sometimes a sign of the faction that desires Northern Ireland to remain in the union with Great Britain.