Civil Wars are wars between groups or regions within the same territory/state/country.
The conflict in Syria is a good example of a Civil War (image taken from activistpost.com)
Rebellions are an uprising or organized resistance to a current government
The conflict in between the MILF and the government in Mindanao is a good example of a rebellion.
Revolutions are an overthrow of the current government in favor of a new government. A change is necessary for a revolution to occur.
The EDSA People Power Revolution in the Philippines was a good example of this.