"Col." is a written abbreviation for Colonel.
As an abbreviation, "Col." is primarily used as a title preceding a person's name to denote their rank in the military or, in some cases, honorary positions. For example, you might see "Col. Smith" used to refer to Colonel Smith. The purpose of the abbreviation is simply for brevity. It's commonly found in written communications, official documents, and news reports where space might be a concern.
