The war in Syria has killed about 300,000 people since 2011. The fighting continues between about 200,000 government forces (soldiers, Hezbollah gunmen from Lebanon, local pro-government militias and Shia militias of foreign volunteers recruited by Iran). Facing the government forces are over 100,000 rebels. There is no precise count because there so many rebel factions and some of them are just local defense forces which become pro-rebel or pro-government as needed. There are probably at least half a million armed men (including a few women) in Syria but many have no interest in fighting.
About ten percent of the rebels are foreigners, mostly with Islamic terrorist groups. The problem with the rebels is that they are split into over 500 separate groups. The largest single rebel group is ISIL (Islamic State in Iraq and the Levant), who comprise about 30,000 gunmen. There are about as many less-radical Islamic terrorist groups, most of them (like al Nusra) allied with al Qaeda and often fighting against ISIL and the government. About half the rebels are less radical but most are “Islamic” to one degree or another. About 20 percent of the rebels are not very religious and about half of these are Kurds (most are Sunni Moslems but not fanatic about it).
Many of the rebels are defending a specific area. Hezbollah holds positions on the Lebanese border, striving to keep the war out of Lebanon. Many pro-government militias are static and defending their home areas, especially in western Syria. Some of the Sunni Arab tribes in eastern Syria are still fighting ISIL while others are neutral.