ETF vs. action

Une action, c'est une seule société ; un ETF, c'est un panier. La transaction se ressemble, le profil de risque non.

Buying a stock means owning a piece of one company; your outcome depends on that single business. Buying an ETF means owning a basket — sometimes thousands of securities — so no single company's failure can wipe out the position. The trade itself looks identical: both have tickers, bid/ask spreads, and intraday prices.

The trade-off is concentration versus diversification. A single stock can multiply many times over or go to zero; a broad ETF will roughly track its market segment. Sector and thematic ETFs sit in between — diversified across companies, but concentrated in one industry's fate.

ETFs also charge an ongoing expense ratio, which individual stocks do not. For most ETFs this is small (often a few hundredths of a percent), but it is a real cost of the packaging.