99% of the travertine which you see online or displayed throughout retail locations such as flooring companies, pool builders, home improvement companies etc. is by default cross cut. This refers to the default way of cutting the travertine blocks which are harvested from the quarry. In order to produce vein cut travertine, the travertine blocks are rotated and the cuts take place across the vein. Think of it as cutting a tree. You can cut a tree vertically or horizontally. If you cut it vertically, the veins come out, same with Travertine.
Travertine slabs refer to large pieces of Travertine which are i.e. custom cut with CNC machines to produce counter tops. Travertine slabs are usually 2-5 cm (centimeters) thick. The width of a slab is up to 67", the length of a travertine slab is up to 115". Travertine slabs are usually exported by the bundle.