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In set theory, a universal set is a set which contains all objects, including itself.

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In set theory, the complement of the set A is the set of elements of the universal set that are not elements of A.

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The difference of two sets, written A-B, is the set of all elements of A that are not elements of B.

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In set theory, a cartesian product is a mathematical operation that returns a set from multiple sets. That is, for sets A and B; the cartesian product A x B is the set of all ordered pairs where a belongs to A and b belongs to B.

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A set is a well-defined collection of distinct objects. The object can be anything: numbers,people,letters of the alphabet...

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There are 3 ways to represent a set:
-tabular form:A=(1,2,3,4...)
-descriptive form:A=set of first 5 natural number
-set builder form:A=(x/X maggiore di 5)

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In the intersection, the final set is composed by the common elements of A and B.

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In the union, the final set is composed by all the elements of A and all the elements of B.
His symbol is U

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set theory is a branch of mathematics that deals whit the properties of well-defined collections of objects, which may or may not be of a mathematical nature, such as numbers or functions.