NOMADS are members of the Club who travel chapter-to-chapter. They're considered another chapter on their own, and are usually 'deployed' to Chapters. (In most MC's in SA:MP this rank is reserved for inactive/reserve members as it gives them IC reason to be)
Their duties include.
Deploying to any Chapter when asked to by Nomad President or National President.
Although another chapter, must still follow directions of their Hosting President (President of whichever club they're visiting)
Deployed to help in conflict, or investigate mishappens (Eg: President stealing money from Club Coffers)