Salut Rebecca,

Qui est-ce qui  -> who is it who ...

Qui est-ce que -> who is it that ...

To supplement the standard excellent lessons, sometimes it helps to have a slightly different explanation.

This is why I have included the following link to Laura Lawless's grammar explanation:-

https://www.lawlessfrench.com/grammar/que-and-qui/

I hope it helps to explain further for you.

Bonne continuation,

Jim