Funds and market indices, without the jargon
Understand what an index measures and what an investable fund actually owns.
Diversification changes the dependency
One company outcome can be dominated by one management team, balance sheet or industry event. A wider basket spreads those company-specific outcomes.
Use this as a decision check
Can you explain both the purpose of the money and the downside without relying on a recent return?
A basket can still fall
Diversification reduces concentration risk, not market risk. Fees, inflation, currency and the actual holdings still matter.