In many countries and jurisdictions, it is legislated (by law) that a marriage is legally recognised only after the marriage vows had been administered by a person licensed to administer such vows.
In many countries and jurisdictions, a religious minister could apply to be a licensed marriage officiator to legally administer marriage vows. However, many couples in such countries either are unable or prefer not to have their marriage administered by a religious minister. In such cases, their marriage could be administered by the city clerk, mayor, justice-of-peace (perhaps, the police chief even?) or any civilian government official allowed by law to administer marriages. Such marriages are said to be officiated by a civil official, and are usually termed civil marriage or civil ceremony.
There are rare jurisdictions where anyone could administer marriage vows where the marriage would be legally recognised (Montana, for instance). However, such marriages if not officiated by a civil government official or by a religious minister would be a civil marriage but not officiated by a civil official but by a civil person. (What if the marriage was administered by a friend who happened to be an off-duty soldier?)
Therefore, civil marriage rituals are usually differentiated from religious marriage rituals by not being administered by a religious minister.
OTOH, if a couple (of soldiers) wish to be married not by a chaplain (religious officer in the military) but by a superior officer, such marriages would not be considered a civil marriage since they are not officiated by a civil official of the government but by a marshal official of the government.