Sets contain only unique values?

Question

In this question I was confused. Maybe it could be not 'values' but 'keys'?

Answer 1

I think we use key to get value from Map.
But Set contains only values, so it does not need key.

Answer 2

sets contain only unique values. we can't have duplicate values in a set. it's just same as sets in mathematics. it refers to values or rather data we enter, not the key.

Answer 3

In normal sets values are the same if equals () returns true and in hashsets if the hashcode is the same, I think

Answer 4

hashset is the implementation of set. and every hashset element is associated with unique hashcode