What does "one sec" mean? And is it always interchangeable with "wait, hold on"?

Native speaker’s answer
Rebecca
"Sec" is a shortened version of the word "second". The expression "one second" means "one moment" or expresses to wait for awhile. So "one sec" or "one second" is always interchangeable with "hold on". Ex: One, second, I need to find my wallet before we go. Ex: Hold on one second, I have to take this call.