ETFs, bonds, REITs, in normal-person English

You keep nodding at words like ETF, REIT or covered call without quite knowing what they mean. This explains the concept as if to a smart fifteen-year-old, runs one concrete example with real numbers, and names the misconception people usually carry about it. Plain English, no jargon hiding the gap.

Explain [concept, for example, ETF, REIT, covered call] like I am 15 but smart. Use one concrete example with real numbers. Then give one common misconception people have about it.