In Ireland during the C18/19's the majority of Irish people lived in rural areas and were engaged in agriculture, on the great estates.

Many were small tenant farmers on the estates, which were mainly owned by Irish and Anglo -Irish families and landlords, many of them were absentee landlords.

Estate records can provide information on tenants and occassionaly families , account books, maps, leases, rents.

Today so many of the large estates of the past have been broken up, few exist as they were and records have been deposited in repositories arond Ireland.
There are limitations to their value to Family Hisorians. Often a middleman was engaged to sub-lease to others and no records were made of these.
Many small holders were ignored as they had no rights of tenure.. The National Archives in Dublin hasn't catalogued the records making them difficult to research.