yeah I know them - but I don't understand why and what they have against the people there
I know they hate the usual suspects (USA, the west in general, etc) - but what do they have against the people in the region they are slaughtering?
Well, it really is only partly in response to the US/West etc. Labelling it as that is just lazy.
A lot of it is Sunni vs. Shia.
Iran and Iraq are, in essence, the two Shia states in the Middle East and they are surrounded by Sunni states. Trust me, these guys (Sunni and Shia) hate each other just as much, if not more, than "the West".
Iraq is a majority Shia state but Hussein was a Sunni and his minority group rules over the Shia and Kurds with an iron fist. Hussein gets wiped out and the majority Shia come back into power in the new, democratic government.
So do they put their previous oppression aside and forge Iraq into a new, united state with a marshmallow and rainbow future? No, they turn around and slap the Sunni in response to being oppressed by them for the previous 30-40 years.
Daesh is a Sunni uprising, backed largely by those who were previously part of Hussein's minority dictatorship and who want to regain control of the land.
This is where Syria comes in. Syria is the reverse of Iraq - a majority Sunni state ruled over by a Shia minority (Assad being the Shia puppet of the Shia Iranians), so Daesh can cross the Iraq/Syria border and find an oppressed Sunni majority ally.
Shitfight ensues.
The rest of the Middle East aren't going to do much about it - they're Sunni, too, just like Daesh and the majority, oppressed Syrians. So they put in token efforts so that the US doesn't get the shits but they don't really commit.
They also use the chaos to push their own, largely Sunni-based, agendas.
Turkey have a southern border with the north of Syria. That Turkish/Syrian border is populated by the third ethno-religious group of the region, the Kurds (who also live in the northern part of Iraq, and they were hammered by Hussein, too, because everyone f**king hates the Kurds). So, under the guise of "helping fight Daesh", Turkey smack northern Syria, but really they just want to smack the Kurds.
Similar with Saudia Arabia. They have a puppet Sunni regime in Yemen, so they're waging their own shitfight amidst the chaos against the third group there, the Houthi. Yemen has a f**kload of oil but the Saudis don't want Yemen becoming rich and independent cause then they could do something with that oil and the Saudis place at the top of the oil food chain would come under threat. So they continually f**k with Yemen and take the opportunity of Daeshian chaos to smack the Houthi around.
Iran are in the fight for two reasons - the Shia/Sunni divide (Iran are Shia whereas Daesh are Sunni) but also because they see the opportunity to expand their hegemony, possibly by getting influence with the now dominant Shia faction in Iraq. This is not good for anyone...well, except maybe the Iranians...
It's all a big shitfight based around ethno-religious variances that go back over a thousand years. Everyone has their "side" and plenty have puppets (Iran has Hezbollah and Syria, for example, while the Saudis have Yemen)
*****
Just in case anyone wants a distinction between Sunni and Shia...
In essence, both are theocracies but they have a differing opinion on how their leader, or Caliph, is chosen.
Sunni - Kind of the democratic version of Islam. While this isn't exactly true, a simple version is their leaders are kind of "elected" in the same way the Pope is - by religious leaders choosing him.
Shia - Kind of like the monarchy of Islam. They believe the Caliph is descended through the bloodlines of Mohammed and there is no "election".