If you visit Shanghai for tourism, you need a tourist visa; if for business, then, you need to apply for a business visa. A tourist visa invitation should be from a Chinese tour agency or an invitation letter from China if you have relatives to be visited in China. For business, an official invitation from related Chinese government departments or companies / organizations authorized by Chinese Ministry of Foreign Affairs is required. The invitation letter contains your name, address, position, travel date, intended stay period and travel itinerary, etc.