Validity
The visa is valid for three or six months from the date of issue. If for example you have a visa valid for three months, the visa will become unusable if you don’t enter into China within three months of the issue date (this is the reason that you don’t want to apply for a visa too soon).
Number of entries
The number of times you can enter and exit China with the same visa. If you have a single entry visa, this will expire automatically once you leave China (note that visiting Hong Kong or Macao counts as leaving the country).
Stay
The number of days you can stay in China (starting from the day you enter the country). For a tourist visa the stay is a maximum of 60 days.