They are control key sequences that are arranged so that a typist need never remover their fingers from the keyboard. The control key was to the left of the A so easily pressed with you left little finger.
You had full control of the cursor without the need for dedicated arrow keys or page up and down keys. It worked on a normal terminal keyboard. I first used it on an Apple ][ with a Z80 add-on that ran CP/M.
That's true-ish. But the thing about Wordstar is that it is a word processor not a text editor. Other word processors don't make this so easy. Also the standard keybindings for cursor control in Emacs are much less ergonomic.
^ = control
In Wordstar: ^S/^D moves left/right; ^E/^X moves up/down; ^A/^F word left/right; ^R/^C moves page Up/Down
Notice that all of those use only the left hand. In Wordstar almost everything to do with cursor control uses only the left hand.
Emacs is mnemonic ^b for left (back), ^f for right (forward), ^n for next line, ^p for previous line, etc. You need both hands and the keys are all over the keyboard.
You had full control of the cursor without the need for dedicated arrow keys or page up and down keys. It worked on a normal terminal keyboard. I first used it on an Apple ][ with a Z80 add-on that ran CP/M.