Distinguishing Between Arguments and Explanations

While the two can functionally be used interchangeably and combined, the intent behind each determines the context and the context is what makes the difference.

An explanation provides background information to facilitate understanding, and an argument is meant to persuade. In some cases the explanation is being provided to facilitate understanding of something that has already been accepted as true. In the case that an explanation is offered by a discussant and the other participating discussant knows the explanation can't be correct, then the context can shift and argumentation can proceed.

Explanation  Information that is supposed to indicate the origin, cause, meaning, or significance of an event or other phenomenon.
Example: "She's the best tennis player on the team because she has had better coaching, is in better shape, and practices a lot more than anyone else"

Argument  Information that is supposed to establish that a proposition is true or otherwise worthy of belief or acceptance.
Example: "She consistently defeats all her teammates, so she's the best tennis player on the team."
Ralph H. Johnson, J. Anthony Blair. Logical Self-Defense. New York: IDEA, 2006. 18-19.