Difference between Nightmares and Sleep terrors: you typically remember your nightmares - maybe not every detail, but you can remember that you’ve at least had one.
But with night terrors, you could wake up and have no idea it occurred. The episode is typically remembered by your bed partner (hard for them to sleep through the screaming!), but not by you. So, if you sleep alone, you could have sleep terrors and not even know it.