Boko Haram, the group of militant extremists in Nigeria, have grabbed headlines in the past week thanks to their brazen kidnapping of 275 girls, aged between 16 and 18, from a boarding school in the town of Chibok on April 14.

After the group admitted to being responsible for the mass kidnapping, they abducted eight more girls, aged between 12 and 15, from the town of Warabe, also in the Borno state where Chibok is located, on Sunday.

Read on to learn the essentials about the group and its violent struggle in Nigeria.

1. "Boko Haram", loosely translated, means "Western education is forbidden" in the Hausa language. It is actually a nickname bestowed by people in the city of Maiduguri, where the group has its headquarters. The group's official name is actually Jama'atu Ahlis Sunna Lidda'awati wal-Jihad, which means "People Committed to the Propagation of the Prophet's Teachings and Jihad" in Arabic.

2. Boko Haram was founded in 2002 by a charismatic Muslim cleric, Mohmmed Yusuf, who set up a school and a mosque in Maiduguri. He quickly attracted a following in the region, where Muslims perceived themselves to be discriminated against by the Christians. The movement's popularity was also driven by the population's frustrations over endemic poverty and systemic corruption. Distrust of the West is also an historical legacy in the north-east, dating back to the early years of the 20th century when the British gained control over the Sokoto caliphate which then ruled the area.

3. Boko Haram's aim is to overthrow the government and install an Islamic state that will implement syariah law. Nigeria, which has a population of 175 million, is divided between a Muslim-dominated north and a Christian-majority south. To achieve its aim, the group has organised gun attacks as well as bombings in 2009 which drew national and international attention.

4. The high profile violence led to a government crackdown in Maiduguri, with street shoot-outs and hundreds of Boko Haram supporters killed. Nigeria's security forces stormed the group's headquarters, capturing and then killing Yusuf, whose body was shown on state television. The Nigerian government then pronounced the movement dead, a not-unreasonable assumption given the death of its leader.

5. A mysterious successor, Abubakar Shekau, emerged to take over Boko Haram. Very little is known about him, but under his leadership, the group has become even more militant and violent. And he proved the Nigerian government's claims that he was dead to be exaggerated when he popped up in propaganda videos. His latest appearance was in a video in which he claimed responsibility for the recent mass kidnapping and declared that he would sell the girls.

6. The group's latest trend in raiding villages and kidnapping girls is an abhorrent practice. But, in a recent BBC report, African affairs analyst Jacob Zenn pointed out that Nigerian security forces kickstarted the vicious circle by taking prisoner the wives and children of Boko Haram members as a way of pressuring the group.

7. Nigeria's military has also been accused of incompetence and of escalating the violence with questionable methods which include summary executions and rape. The military is ill-equipped to deal with the insurgents who are supplied with better weaponry, are better trained and well-funded.

8. The dilapidated structure of Nigeria's government has also allowed Boko Haram to flourish with little interference. A measure of the lack of infrastructure and information can be seen in how long it took for news of the April kidnapping to reach the world, and the confusion over exactly how many girls were snatched. To date, the Nigerian government has been unable to confirm the names of all the missing girls.

9. Little is known of how Boko Haram is funded, where its members are trained or even how big it is. But the United States government officially labelled it a terrorist group in November 2013 and put a US$7-million bounty on Shekau. The US also said that the group has ties to the Al-Qaeda affiliate in West Africa as well as extremist groups in Mali.

10. The group's latest actions included a bus bombing in the capital Abuja which killed 70 people. But the kidnapping might be the straw that breaks the camel's back. There has been a wave of protests in Nigeria as citizens took to the streets to show their anger at Boko Haram and vent their frustrations at President Goodluck Jonathan's inability to find and rescue the girls. A Twitter hashtag #bringbackourgirls has also been trending, alerting the outside world to what has happened. And Shekau's threat to sell the girls seems to have finally galvanised other powers into offering the beleaguered country help to deal with the urgent matter of finding and rescuing the victims.

Sources: BBC, CNN, The Independent, Los Angeles Times