Most performers include "riders" to their contracts with a venue. Riders in performance contracts are much the same as riders to insurance policies: they provide for special requirements that cannot easily be put in the main body of the contract. In performance contracts riders are used to provide for stuff backstage and to set the technical requirements for the performance itself.
Usually, they are interesting if only to provide a glimpse into the mandarin proclivities of people in the music business. Follow the link below to read the rider to a contract for a performance by the legendary Iggy Pop and the Stooges which was written by one of his techies and obtained by the good people at The Smoking Gun. This one is unusual in that, unlike most contract documents, it is screamingly funny.
It is hilarious even if you don't know the first thing about lights and sound equipment.