About Visa

A China visa is a permit issued by Chinese visa authorities (Chinese Embassies, Chinese Consulates, Chinese visa offices or Public Security Bureau) to non-Chinese citizens for entry into and transit through China mainland (Hong Kong SAR and Macau SAR have different visa systems). Citizens of most countries are required to obtain Chinese visas before entering China mainland. There are eight categories of ordinary China visas, which are respectively marked with the letters C, D, F , G, J-1, J-2, L , X and Z .Before you enter into China mainland, you can apply for a China visa in the Chinese Embassy in your country or where you stay. When you are already in China mainland, if you want to stay longer, you don't need to exit from China mainland to apply for a new China visa. Instead, you can have your visa extended or converted through a visa agent.The Chinese visas issued by Chinese Embassies (Consulates or visa offices) have limitations of each stay (e.g. 030, 060, 090, 120, or 180 days). Make sure you yourself enter before the date mentioned on the Chinese visa. And don't overstay your visa since the limitation of each stay is calculated right from the entry date (the red oval stamp you get on your passport when you enter into China through customs).

Do I need a Chinese visa ?
If you want to travel to Mainland China, whether for business or tourism, you are required to have a Chinese visa obtained from a consulate in advance of your trip.
You are exempt from applying for a Chinese visa if you travel and stay only in Hong Kong or Macao for some days.

I am going to mainland China, then to Hong Kong and back to mainland China. Does this mean I must have a double-entry visa?

Yes. Although Hong Kong SAR and Macau SAR are part of China, they have different visa systems from China mainland. Each time you enter into China mainland, one entry will be used up.
http://www.immd.gov.hk/ehtml/hkvisas_4.htm
http://www.dsi.gov.mo/announcement/E002_index.html

If I want to stay longer in China, can I have my visa done without leaving China mainland？
Yes.
If you are holding an L visa, technically you can have it extended twice, with 30 days of each time. If you want to stay longer even than that, you can have your China visa converted to an F visa through a Chinese visa agent.

I got the China visa at the embassy. What does this visa mean?

CATEGORY: L (tourist visa or visiting relatives) - there are other types, such as F (for business or short-term study), X (student visa), Z (work visa)
ENTRIES: 01 - there are other types, such as 02, M (multiple) and 00.
DURATION OF EACH STAY: 090 - there are other types, such as 030, 060, 120, 180.
ENTER BEFORE: 23FEB2006 and ISSUE DATE: 23NOV2005: 3-month visa

If you enter into China mainland before Feb. 23, 2006, you can use this visa. The 90 days of duration of stay is calculated right when you enter into China mainland through customs. Suppose you enter on Jan. 3, 2006, the visa is valid until April 2, 2006.

And if you want to go to Hong Kong and return to China mainland on Feb. 12, 2006, you cannot use this visa though it is still ENTER BEFORE Feb. 23, 2006. The only 1 entry has been used up the first time you enter. If it were a 02-entry visa, you would use it again.

The China visa include:
C Visa (Crewmember Visa): Issued to crewmembers on international aviation, navigation and land transportation missions and their accompanying family members.

D Visa (Residence Visa): Issued to foreigners who are going to live in China permanently.

F Visa (Business/Visit Visa): Issued to foreigners who are invited to China for a visit, research, lecture, business, scientific-technological and cultural exchanges or short-term advanced studies or intern practice for a period of less than six months.

G Visa (Transit Visa): Issued to those people who transit through China.

L Visa (Tourism Visa): Issued to those who enter China temporarily for touring, family visiting or other personal affairs.

X Visa (Study/Student Visa): Issued to foreigners who come to China for study or intern practice for a period of six months or above.

Z Visa (Work Visa): Issued to foreigners who are to take up a post or employment in China, and their accompanying family members.

J Visa (Journalist Visa)

China Travel Visa
China Travel and Touring Visa (L)

Tourist or Travel visas are issued to aliens who come to China for sightseeing, family visiting or other private purposes. They are easy to obtain and require no special documentation other than your passport, photo and completed Q1 form. They cannot be used for working in China or for conducting business or operation of remote offices in China. However you can use tourist visas to visit China for seminars and networking events such as conventions and trade fairs. You can stay in China between 30 to 90 days for each entry.