A: I've never had this kind of crab before. What's it called?
B: It's a mitten crab. It's called that because of the fur on its claws.
A: There doesn't seem to be a lot of meat.
B: No, we eat it mainly for its roe.
The roll has salmon roe in it.
The roe is the best part of the crab.
What's something called?
A: What's that thing that opens the wine bottle called?
B: It's called a corkscrew.
A: How do you have so much free time?
B: It's called being unemployed.