What's the difference between a fund's ticker and its CUSIP, and which do I use to buy?

For buying, you'll almost always use the ticker — the short letter symbol like a five-letter mutual fund code or a three-letter ETF symbol that you type into your brokerage to place an order. A CUSIP is a nine-character identifier used behind the scenes to uniquely tag a security in the financial system; you rarely need it, though it can help confirm you're buying the exact right fund when several share similar names. Be careful with tickers: a single fund family may offer the same strategy in several share classes, each with its own ticker and its own expense ratio. Match the ticker to the specific low-cost, no-load share class you intend to buy, not just the fund name. When in doubt, cross-check the ticker against the fund's official fact sheet before placing the order.