"Hamas" is an Arabic acronym that translates to Islamic Resistance Movement. It was formed in 1987 by Sheik Ahmed Yassin, a former leader of the Muslim Brotherhood.
Yassin established a rhetoric of lauding the martyrdom of suicide bombers and other jihadists who acted in the interests of establishing Israel as a nation belonging to Islam.
Hamas is very different from other terrorist groups due to its strong nationalist presence, government rule in Gaza, complex infrastructure, and terrorist tactics.
Daniel Ayalon, Israel’s former U.S. ambassador, said on NPR, "They send terrorists strapped in explosives into markets [...] coffee shops, and into school buses and kindergartens."
Hamas' business presence in Gaza has made it an unavoidable part of everyday life. Its income gets rolled over into more of its assets, which means more income for Hamas.
In 2018, ISIS actually declared war on Hamas for not prioritizing God's law when they got involved in elections, and for their communications with Egypt and Iran.
Columbia University's Tareq Baconi told NPR, "The two are not allies [...] to even put them together as extremist organizations might overlook a lot of [their differences]."
Hamas sets up recruiters in a social services network in mosques and schools that teaches families to value martyrdom and that it’s honorable to have a terrorist in the family.