When switched to "On", Remember and Repeat replicates the standard classroom spelling strategy Read Cover Write Check. A student types a word, it disappears and they immediately type it again from memory, benefitting from the extra repetition.
This is how you find the option in the Settings menu:
It is recommended that this feature is used when a student reaches words that they are finding particularly difficult to spell.
When Remember and repeat is switched on, an icon (RR) will appear on the keyboard screen.
Here's an example of Remember and Repeat working (sound is not recorded)