There are four main groups fighting in the Syrian war. They are Assad and the Syrian government, ISIS, the Kurds, and the rebels. This diagram shows that since the war began, Assad has gained support and resources from Iran, Hezbollah, and Russia. Assad and his army aren't the only group to have acquired support in the war. The rebels have gained support from the Gulf States, Jordan, Turkey, and the U.S, who is also helping the Kurds. ISIS has not gained support from any countries so far since they joined in the war.
The people of Syria started peaceful protests when Assad didn't change the way the government treated the people. They started their protests to support democracy so that Assad would get the message to honor his original promises of helping the people. Assad quickly took offense and turned his military on the protesters in March of 2011. But by June of 2011, some of Assad's troops decided that the protesters should be protected instead of killed and left Assad's army.
Countries from around the world have been very worried of the outcome of the Syrian war. The war has caused countries to get involved and multiple countries were so worried about the war that they have asked Assad to step down so it doesn't spread throughout the rest of the world. Both Lebanon and Jordan are very worried that the Syrian war will invade their countries, especially because they are predominantly Muslim countries.
Assad has been favoring people of his own religion, Alawite which is a Shia Islamic sect, as well as his ethnic group since the start of his control over the country even though the majority of the country is Sunni. Because both Jordan and Turkey are Muslim they have become very worried from the close proximity of the war.
The war has caused such a large percent of the Syrian population to move. About fifty percent of Syria's population has been displaced due to the war.
Although a large percentage of the Syrian population has been forced to move, this number would probably be higher if not for the causalities. Over 450,000 Syrians have been killed and over 12 million have been injured. Of this large amount of tragedies, a lot of them are civilians. This doesn't even include the hundreds of imprisoned protesters.