A container word is usually connected to an uncountable noun, to form a countable amount.
For example, butter is uncountable, but we can count STICKS of butter or PACKETS of butter. So, stick and packet are container words.
We also use container words with some countable nouns. For example, we can say a BUNCH of grapes or a BUNCH of bananas.
Quiz number 52 features 28 container words and has been redone to include images and pronunciation.
You can try the quiz here:
A BUNCH of grapes: