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The union of sets is a fundamental operation in set theory, which combines all unique elements from two or more sets into a single set. When we perform the union of two sets, denoted by the symbol \( \cup \), we're putting together the elements from each set without repeating any of them.

For example, if we have Set A with elements \( \{a, g, h\} \) and Set B with elements \( \{b, g, h\} \), their union \( A \cup B \) would include every distinct element from both sets, that is \( \{a, b, g, h\} \). Here, although \( g \) and \( h \) are present in both A and B, they appear only once in the union set.

It's useful to remember that the union of sets resembles the 'OR' logic in Boolean algebra where an element is included if it exists in either of the sets.

The intersection of sets, represented by the symbol \( \cap \), is another core concept in set theory which identifies common elements that are shared between sets. When you find the intersection of two sets, you are essentially finding what they have in common.

Taking our previous example where the union of Set A \( \{a, g, h\} \) and Set B \( \{b, g, h\} \) was \( \{a, b, g, h\} \), the intersection of these two sets, denoted by \( A \cap B \) would only include \( \{g, h\} \) since these are the only elements present in both A and B. Intersection correlates with the 'AND' logic in Boolean algebra, signaling that an element has to be in both sets to be included in the intersection.

Venn diagrams are an incredibly useful tool in set theory for visualizing the relationships between different sets, such as their union and intersection. A Venn diagram consists of overlapping circles where each circle represents a set, and the regions where the circles overlap show the intersection between the sets.

For instance, we can represent Set A \( \{a, g, h\} \) and Set B \( \{b, g, h\} \) as two circles that overlap in areas \( g \) and \( h \) to demonstrate their intersection. If we add another Set C, we create another circle that overlaps with A and B, producing various regions of intersection. By shading the relevant areas, we can depict \( A \cup B \) or \( A \cap B \) visually, making it easier to comprehend complex set relationships at a glance.

Venn diagrams are particularly helpful when dealing with an exercise like the one provided, as they provide a clear and immediate visual representation of both the union and intersection of sets.