OverwriteTarget
is an option for functions like CopyFile that specifies whether to overwrite if target files already exist.
Examples
Basic Examples (1)
Copy the file to a new location:
Copying the file back fails with OverwriteTarget->False:

Use OverwriteTarget->True to overwrite the existing file:
Text
Wolfram Research (2016), OverwriteTarget, Wolfram Language function, https://reference.wolfram.com/language/ref/OverwriteTarget.html.
CMS
Wolfram Language. 2016. "OverwriteTarget." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/OverwriteTarget.html.
APA
Wolfram Language. (2016). OverwriteTarget. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/OverwriteTarget.html