Official Sinn FéinOfficial Sinn Féin
evolved from the split in Sinn Féin
and the IRA
that took place in the late 1960s. The leadership of both Sinn Féin and the IRA had developed a Marxist
outlook that became unpopular with many more traditionalist nationalists/republicans who formed the Provisional Sinn Féin
and Provisional IRA
For a fuller history of this period, see the aritcle Sinn Féin.
The Officials gradually stepped down their military campaign against the United Kingdom's armed forces presence in Northern Ireland and focussed on electoral activity.
Official Sinn Féin evolved into the Workers Party which has had some electoral success in the Republic of Ireland but little in the North, although they still do contest some seats. It is now more of a Marxist party than a Republican one and is avowedly non-sectarian.
Provisional Sinn Féin is the party that is now commonly referred to simply as Sinn Féin and they have had much greater electoral success than the Official wing.