Answer:
Choanoflagellate are organisms while choanocytes are cells.
Step-by-step explanation:
Choanoflagellates are very old marine organisms that resemble a lot to the cells found inside the Porifera (sponges) called the choanocytes. The shape is very similar and has the flagella that characterize them. It's not clear yet how sponges got to develop such cells but they're useful for them in order to eat and absorb nutrients.