Otta I should have explained it better, my fault, but on a permanent site it is for an open-ended ended (in perpetuity if required) stay/residency. A "pitch" can typically accommodate 3 or more homes eg: caravans to enable the extended family to be together. A transitory site is for just that, a short stay. The terminology refers to the type of residency, all sites become permanent, in that regard, as a legal provision.