Can anyone please explain to me the difference between Irish and Celtic?

There are generally six Celtic peoples recognized in the world today. They divide into two groups, the Brythonic (or British) Celts, and the Gaelic Celts. The Brythonic Celts are the Welsh, Cornish and Bretons; the Gaels are the Irish, Scots and Manx (inhabitants of the Isle of Man). Some people recognize a seventh Celtic nation in the region of Galicia in Spain (their Celtic language died out a thousand years ago, and so the Celtic links are more tenous).

If something says Irish it means something found in Ireland period. If it says Celtic it could be from anyone of the celtic nations.

the Celts are an ancient tribe of peoples from greater germany and europe. A percentage of them migrated over time to the modern day brittish Isles.

To say that the Irish or scottish are celts is incorrect. The Isles peoples are a mixture of the various invaders of the last few thousand years from various parts of mainland europe and the nordic cultures in various waves over time. Some integrated (various nordic cultures contrary to popular belief) and others conqoured (romans).

The celtic tradition is more a social movement if you will that provided much history, mythology and art. If for instance you look at the Irish Catholic tradition Celtic Crosses etc come from the Celtic culture as most of the catholics there were not fly ins but locals from the various backgrounds. Unlike many other parts of the world Catholicism merged with older traditions in Ireland rather than replaced them.

Celtic includes Ireland, Scotland, Wales and Brittany. Also, the ancient Celtic people used to live across a massive area of Europe and Asia. They were pushed back more and more by the Romans, then by the Angles and Saxons and other Germanic tribes to the point where they were only in the British isles.

Celtic can also be Welsh, or Scotish