What is the difference between a Superset and a StrictSuperset (Subset and a StrictSuperset)? Please answer.

Question

Set membership and equality in Swift

Answer 1

That is compareable to < and <=.
Each set is a subset and superset of itself, but never a strict one.
With other words: Set A is a subset of B if for any element a of A a is also an element of B.
A is a strict subset of B iff additionally there exists at least one element b of B which is not an element of A.

Answer 2

A set A is said to be a subset of a set B; if and only if, every element of set A is also an element of set B. Such a relation between sets is denoted by A ⊆ B. It can also be read as ‘A is contained in B’. The set A is said to be a proper subset if A ⊆ B and A ≠B, and denoted by A ⊂ B. If there is even one member in A that is not a member of B, then A cannot be a subset of B. Empty set is a subset of any set, and a set itself is a subset of same set.

If A is a subset of B, then A is contained in B. It implies that B contains A, or in other words, B is a superset of A. We write A ⊇ B to denote that B is a superset of A