A cairn is a large pile of stones, quite often (but not always) containing a burial. Sometimes they have a kerb around the base.
Most cairns are hemi-spherical (like half a football), but the piles of stones used to cover wedge tombs , court tombs and portal tombs are also called cairns. When associated with these types of monument they are not always round, but sometimes rectangular or trapezoidal.
A kerb is a ring of stones placed around the perimeter of a burial mound or cairn. It basically serves the purpose of a retaining wall to keep the cairn or earth in place. Kerbs are usually associated with passage tombs, but do occur on court tombs and wedge tombs too.
Sometimes on passage tombs the stones can bear decoration, such as at Newgrange (County Meath).
One of the most fascinating types of remains left to us by our neolithic ancestors. Enigmatic carvings on rocks, either loose boulders or earth-fast rocks. Designs vary enormously from simple cup marks to amazing spirals, zig-zags, checker-board and lozenge patterns.
No one knows what these symbols once stood for, but many theories exist including star charts, calendars and maps. Many passage tombs are adorned with rock art, both inside the chamber and on the kerb.
In wedge tombs and court tombs the burial compartment is known as a gallery and collectively wedge and court tombs are called classified as 'gallery graves'. This is because the inner area is long and narrow, i.e. bascially rectangular, in plan.
In court tombs the gallery is usually divided into two or more chambers by jambs. Wedge tombs are segmented by sill stones, as are a few court tombs.
Two stones place either side of a gallery, opposite each other, but not touching so as to leave a gap, that are used to segment it into smaller chambers.