WHO WILL VOTE?
Some 10.5 million Afghans are registered for the election. Women make up 41 percent of registered voters.
Afghan refugees living in Pakistan and Iran are expected to represent 10 percent of all votes cast.
The United Nations, which is organizing the polls, says there have been many multiple registrations. Voters will have their fingers marked with indelible ink on election day in an attempt to prevent multiple voting. Actual turnout is expected to be closer to 6 million.
WHO ARE THE CANDIDATES?
There are 16 contenders out of an initial 18 registered candidates.
The incumbent, Afghan Transitional Administration Chairman Hamid Karzai
, an ethnic Pashtun, is widely considered the front-runner.
Karzai's strongest challenger is expected to be Mohammad Yunos Qanuni
, an ethnic Tajik.
Other key candidates include Uzbek commander Abdul Rashid Dostum
; Mohammed Mohaqeq
, a leader of the Hazara minority; and Mas'uda Jalal
, the only female candidate.
WHEN WILL RESULTS BE AVAILABLE?
Partial results are expected by the middle of the week -- around 13 October.
A candidate must receive more than 50 percent of the votes in order to win a first-round victory. If no candidate wins a clear majority on 9 October, there will be a runoff between the two leading candidates. The runoff would likely be held in November.
Karzai is expected to win, but the large number of candidates may make it difficult for him to win in the first round.
A runoff could give Taliban rebels and other Islamic militants more opportunities to disrupt the democratic process in Afghanistan. Regional warlords who oppose a centralized government are also seen as a threat to peaceful elections.
A runoff could also compromise Karzai's authority and give him less freedom in selecting his cabinet.
WILL THE VOTE BE SAFE?
Militants and other elements have vowed to disrupt polling. At least a dozen election workers have died so far in a string of attacks.
Security issues are considered most pressing in the country's south and southeast.
Some 18,000 U.S.-led troops in Afghanistan battling militants will participate in securing the vote.
Another 9,000 NATO-commanded soldiers in the International Security Assistance Force (ISAF), will patrol in the capital, Kabul, and much of the north.
They, together with some 60,000 Afghan police and troops will be fanning out to protect the roughly 5,000 polling stations throughout the country.
WHAT ARE THE ISSUES?
Ethnicity is likely to be a crucial factor in most Afghan votes.
Widespread illiteracy and limited campaigning by the candidates means few Afghans are familiar with all 16 candidates or their political platforms.
But general issues of concern include improving security, reducing poverty, and speeding reconstruction.