The Bronze Age was the time between the Stone Age and the Iron Age. Bronze is a mixture of tin and copper. Bronze is harder than stone or either of the metals (tin and copper) from which it is made. Because bronze is stronger it could be used to make stronger tools and weapons. These discoveries led to improvements in the way people lived their lives.
The Bronze Age was happening in Europe around 4000BC. But it did not begin in Ireland until settlers came from France arrived in Ireland around 2000BC. They knew how to make tools and weapons from bronze. They taught the Irish how to do this.