I've seen confidence intervals constructed using $\pm 1.96 *SE$ and $\pm 1.96*SD$. Sometimes, the SD is either the (possibly estimated) population or sample SD. When is each one used?
You would use the standard error. Standard deviation has a tragically similar name but is a somewhat different idea.
(They’re related, just not in a way that makes much sense to someone who is just starting with statistics.)
You will go on to learn situations where $1.96*SE$ stops being the way you construct confidence intervals, but $1.96*SD$ won’t come up. That’s just wrong, and as my comment indicates, I am curious where you read that.