Quantum decoherence is a process that explains how quantum systems lose their unique properties when interacting with their environment. In the quantum world, particles can exist in multiple states at once, known as superposition. However, when these particles interact with surrounding particles or fields, they begin to behave more classically, collapsing into a single state. This transition from quantum behavior to classical behavior is crucial for understanding why we observe definite outcomes in experiments. Decoherence helps explain why we don't see superpositions in everyday life, as the constant interactions with the environment effectively "measure" the quantum states, leading to the classical reality we experience.