These three belong to three different clubs.
First one, very popular, is the singles-only club. It is closed for new membership.
Second one, very useful, is for singles and couples. It is open for new members but it is very hard to get in now.
Unlike the first two clubs, the third club is different for these three. The three singles are related to each other. Especially, two of them are talked about constantly and daily.
Outside these clubs, when the three come together, you are looking at very popular food!
Who are they? What are the three clubs?
They are not words