What it teaches
Typing a whole word without losing the place in it — which needs the keys to be findable and the eye to travel between the screen and the keyboard without dropping a letter.
Spelling is not being tested here. The word is right there.
How it works
A short word appears with a keyboard under it. The letters fill in as they are pressed. A wrong key is not accepted and nothing is deleted by it, so no mistake can undo what has already been typed.
What to look for
If a child is fast at Find the key and slow here, the problem is keeping their place in the word rather than the keyboard. Reading the word aloud, letter by letter, before starting to type usually fixes it.