If you are coming to the United Kingdom as a visitor you are allowed to stay for up to six months.
Tourism and visiting friends
If you want to visit the UK as a tourist or to stay with friends in the UK, you should apply to come here as a general visitor (or as a child visitor if you are under 18). If you are a Chinese national and you will be coming to the UK as part of a group for a maximum of 30 days, you can apply for a visa as an ADS visitor.
If you want to visit members of your family in the UK, you can apply to come here as a family visitor (or as a child visitor if you are under 18).
Visiting to do business
If you want to do business in the UK, you should apply to come here as a business visitor (or as a child visitor if you are under 18). This includes academic visitors, and doctors undertaking clinical attachments or the PLAB test.
If you want to come to the UK as a Tier 1 (Entrepreneur), and you need to spend time here first in order to hold discussions and secure funding, you can apply for a visa as a prospective entrepreneur.