What's the difference between an oath and an affirmation?

At a deposition, what is the difference between adminstering an oath vs. an affirmation to the deposed witness?  Are they one and the same or is there some kind of distinction that I'm missing?

I suppose you are referring to this language in the code:

sec. 2025.330(a) “The deposition office shall put the deponent under oath or affirmation.”

The difference between swearing under oath or affirming is slight.  Both methods have the same net outcome, namely, to ensure that the deponent is going to speak the truth; that there is a reasonable expectation about the truthfullness of their testimony.  To some deponents, however, it is an extremely important distinction. Many religions prohibit swearing under oath and thus affirming may be a more pious option.

I've had this once or twice in my 11 year career where a deponent requested to affirm and not swear. I obliged, of course, changing the language in my oath to Do you solemnly affirm...

Now that we've been directed by the CSR Board to eliminate the words swear and So help you God, you don't run in to that much.

I use these very neutral, all-encompasing words... Do you solemnly state...