How to begin? During the negotiations to bring the conflict to an end certain brave men, drivers of Black Taxis, drove through the gates to carry the negotiators and others to the meetings in the Monastery in the Protestant section. Gates? Protestant section? This was our tour as our Black Taxi driven by one of those brave men showed us where the walls are and drove us through those gates. The walls are still up 20 years later and they are the highest barriers you can begin to imagine.
The gates still close at 9 or 10 pm every night. 
The Protestants, Unionists, feel safer separated by the walls from their Catholic, Republican neighbors and vice versa. There is a third area where there is no separation or walls, that is where the educated and well off people live. They too are either Protestant or Catholic, but they live entwined and they intermarry.
The tour ended at The Felons Club.
The credential for membership is being an IRA member and having served time in under the British. We sat for over 90 minutes with three men. A Protestant Unionist, who served 16 years and a Catholic member of Sinn Fein who was a member of the IRA and served 17 years of a life sentence, and a British infantry man who served in Belfast during the troubles. 
These three men who would have been glad to kill each other in 1990 are now able to present there stories to groups like us and to share a friendship that seems unthinkable. None of them think that it is likely to be wide spread in the near future.
Terminology. Unionist wants to remain united with UK (well until Brexit anyhow) Republican wants to reunite Ireland into one country. Ireland is made up of 32 counties. 26 counties make up the Republic of Ireland and 6 are the Irish part of the UK in much the same manner as Scotland and Wales. Just to make it more murky, Ulster is a Province of Ireland and the 6 counties of Northern Ireland comprise 6 of the 8 counties of Ulster. By definition, most Protestants are Unionists and most Catholics are Republicans. They inhale this with their mother’s milk.
Boy, you sure “dug deep” on this phase of your tour!
I remember reading during the reconciliation period after the troubles a quote from a young Protestant: ” I always thought that Catholics had horns”. And he was serious!