Types of sets: (1) Finite: countable elements {1, 2, 3}; (2) Infinite: uncountable {ℕ, ℤ, ℝ}; (3) Empty: ∅; (4) Singleton: one element {5}; (5) Equal: A = B if same elements; (6) Equivalent: |A| = |B|; (7) Disjoint: A ∩ B = ∅ (no common elements); (8) Proper subset: A ⊂ B if A ⊆ B and A ≠ B; (9) Power set: P(A) = all subsets of A. Example: A = {1, 2}. P(A) = {∅, {1}, {2}, {1,2}}. |P(A)| = 2^|A| = 2² = 4. Solving: Identify set classification. Count elements for cardinality. Exam tip: Distinguish ∈ (element), ⊂ (subset). Understand null set is subset of all sets.