The F Visa is issued for visitors and non-commercial activities in China. Generally speaking, people with F Visas are not allowed to gain compensation or income or find a job in China. 

To apply for an F Visa, you might need an invitation letter given by SIOM, CAS headquarters, or the State Administration of Foreign Experts Affairs. 

Foreign experts with invitation letters issued by the State Administrations for Foreign Experts are entitled to work (and be paid and transfer money out of the country) for up to 90 days. The time required to process these kinds of visas is usually longer. 

There are two types of F Visas: single entry and multiple entries, with each stay being less than 90 days. Generally speaking, the validity of multiple-entry F Visas will be less than one year. If you are a high-end talent who has received a National Friendship Award or has been listed in the Thousand Talents Plan or Hundred People Plan, you will be able to apply for an F Visa with a validity period of up to five years.