Al-Shabaab is an offshoot of the Islamic Courts Union (ICU), which splintered into several smaller factions after its defeat in 2006 by Somalia's Transitional Federal Government (TFG) and the TFG's Ethiopian military allies.
Additionally, it attracted some members from western countries, notably Samantha Lewthwaite and Abu Mansoor Al-Amriki.
In August 2014, the Somali government-led Operation Indian Ocean was launched to clean up the remaining insurgent-held pockets in the countryside.
For short, the organization is referred to as HSM, which stands for "Harakat al-Shabaab al-Mujahideen".
The term Shabaab means "youth" in Arabic, and the group should not be confused with similarly named groups.
According to the Jamestown Foundation, Al-Shabaab seeks to exploit these vulnerabilities by manipulating clan networks in order to retain power.
The group itself is likewise not entirely immune to local politics.
Although al-Shabaab's leadership ultimately falls upon al-Qaeda leader Ayman al-Zawahiri, the internal leadership is not fully clear, and with foreign fighters trickling out of the country, its structure is increasingly decentralized.
Ahmed Abdi Godane was publicly named as emir of al-Shabaab in December 2007.
In August 2011, Godane was heavily criticized by Al-Shabaab co-founder Hassan Dahir Aweys and others for not letting aid into the hunger stricken parts of southern Somalia.