the link will explain braided graphite. Dieformed graphite is exactly what is says: graphite formed and produced in dies to form exact geometric figures, for instance flat rings for stem sealings, and often produced from expanded graphite as raw material.
As for all sealing materials, the quality and details of the fabrication process itself, the quality of the raw material and the qulity and amount of mixing with other materials (if any) will give the total end quality for the product (here sealing). This way two sealings with seemingly the same composition, might differ much in quality if the producers are different.
Graphite is often used in combination with other materials (PTFE for instance), and will be present in different amounts in a multitude of sealings, mostly to improve or increase the useable temperature range.
