The Turks very long avoided openly engaging in this conflict, probably hoping to be able to maintain the status quo.
Now they probably realize that conflict is inevitable and decided to deal with ISIS and defeat them.
Correction: Now they have realized that the defeat of the Islamic State is near, and therefore they have decided to deal with the Kurdish Peshmerga directly and defeat them.
I think that Isis made a big strategic mistake here because they created a new great and dangerous enemy.
Turkey has been a great friend of the Islamic State, and it will remain that way till the very end. Earlier, the Turks were just providing weapons and funds to the ISIS barbarians, and allowing the recruits to cross over to the ISIS territory through Turkey. Now they have began targeting the enemies of ISIS in air raids.
This is great news for all others, Kurds, Iraq, Syria etc.
This is a great news for the Islamic State and bad news for normal humans.