At the end of the ballot, the 329 members of parliament elected from party lists will be tasked with forming a government and electing a prime minister and president.

Here is everything you need to know about Iraq's fourth election since the US-led invasion in 2003.

- Voters -

Nearly 24.5 million of Iraq's than 35 million people are registered to vote. They are spread out across 18 provinces.

Voters can cast their ballots at 8,148 polling stations across the country, all of which are equipped for electronic voting.

According to Iraqi authorities, nearly 11 million biometric identity cards have been distributed to authenticate identities.

The 285,564 internal refugees eligible to vote will do so in one of 166 polling stations in 70 camps spread across eight provinces in the country.

Iraqis in the diaspora can also vote in 19 countries.

Voters will select party lists and seats will be divided up according to the number of votes each list secures.

- Candidates -

There are 6,982 candidates, including 2,014 women, set to run in the polls.

They will be competing for 329 seats, including nine reserved for minorities -- Christians, Shabaks, Yezidis, Mandeans and Fayli Kurds -- and 83 for women.

Candidates, selected based on their position in the party, will be elected to four-year terms in parliament.

There are 87 party lists in this year's election.

The main lists are as follows:

- VICTORY COALITION, led by outgoing Prime Minister Haider al-Abadi.

This year, for the first time since the fall of Saddam Hussein in 2003, the ranks of the deposed leader's oldest opponents, the Shiite Dawa Party, are divided.

Abadi, who heads the Dawa Party, has put together a list composed mainly of civil society personalities that cross sectarian lines.

- CONQUEST ALLIANCE, led by Hadi al-Ameri, head of the Badr organisation and leader of the mostly Shiite Hashed al-Shaabi paramilitary units, which played a key role in rolling back Islamic State (IS) group jihadists.

His candidates officially quit their military roles to run for office.

- RULE OF LAW ALLIANCE, led by former prime minister Nouri al-Maliki.

The list relies principally on the Dawa Party, which Maliki led before leaving office in 2014.

But while it is popular with public servants hired under his mandate, the list suffers from criticisms aimed at Maliki because IS seized one-third of the country under his watch.

- MARCHING TOWARDS REFORM, an unprecedented alliance between Shiite leader Moqtada al-Sadr and communists.

It includes mostly secular groups including the Iraqi Communist Party and Istiqama (Arabic for righteousness), a technocrat party backed by Sadr, who suspended his Ahrar bloc and called on his 33 ministers not to run in the polls.

- SUNNIS appear on several lists. The main list, "The National Alliance", is led by Shiite Vice President Iyad Allaqi -- who presents himself as secular -- and Sunni head of parliament Salim al-Joubouri.

Weakened after three years of IS rule, Sunnis could be the biggest loser in this year's elections.

- KURDS will head to polls with divided ranks to fill their northern autonomous region's 46 seats, two of which are reserved for Christians.

The main Kurdish parties are the Kurdistan Democratic Party (KDP) and the Kurdistan Patriotic Union (PUK).

There are also three opposition parties: the main Jamaa Islamiya, the newly created New Generation movement, and Goran (Kurdish for change).