Most major indexes (like the S&P 500) are market-cap weighted, meaning each company's weight in the index equals its market capitalization divided by the total cap of all constituents. That method naturally gives the largest companies the biggest influence on index returns -- which can concentrate risk if a few mega-cap firms dominate performance.

Sequence-of-returns risk matters most to retirees who take withdrawals from a portfolio. Two people may earn the same average return over a period, but the one who experiences large negative returns early while withdrawing income can deplete their balance much faster than someone who sees those losses later.

Bond duration measures how sensitive a bond's price is to changes in interest rates; it's expressed in years and gives a first-order approximation: % price change (duration) (change in yield). For example, a bond with duration 5 will lose about 5% of its price if yields rise 1 percentage point.

International diversification can reduce portfolio risk by exposing you to countries and companies that may perform differently than your home market. But it also introduces currency risk: when you hold foreign assets, the value in your home currency can change because exchange rates move.

Inflation slowly erodes purchasing power: a given dollar buys less over time when prices rise. Investors care about real return (return after inflation) because it shows how much your purchasing power actually grows.

Beta measures how much a stock's price tends to move relative to the market as a whole. A beta of 1 means the stock tends to move with the market; above 1 implies greater sensitivity (higher market-related volatility), and below 1 implies less sensitivity.

Net return after fees can change long-term outcomes. Suppose a fund returns 8.

Volatility is often discussed when people talk about risk, but volatility specifically refers to how much the price of an asset moves up and down, usually measured statistically as standard deviation. Higher volatility means larger swings in short-term returns; that can equal higher potential gains but also deeper losses.

One of the biggest debates in investing is active vs. passive management.

Tax-advantaged accounts are a key tool for investors. Two of the most common are a Traditional (pre-tax) retirement account and a Roth (after-tax) account.

Small differences in fees compound over long periods and can materially change final outcomes. Consider a $10,000 investment held for 30 years: a 7.

Liquidity affects how cheaply you can buy or sell an asset. The bid-ask spread -- the difference between the highest price a buyer will pay (bid) and the lowest price a seller will accept (ask) -- is a direct measure of that cost.

Dollar-cost averaging (DCA) is a strategy where you invest a fixed dollar amount at regular intervals (monthly, weekly) regardless of the asset's price. Over time DCA causes you to buy more shares when prices are lower and fewer when prices are higher, which can reduce the average cost per share compared with trying to time a one-time lump-sum purchase -- especially if prices are volatile.

Rebalancing is the process of returning your portfolio to a target allocation (for example, 70% stocks / 30% bonds) after market movements push weights off target. Over time, some assets may outperform and grow larger in the portfolio while others shrink; rebalancing forces you to sell a portion of the winners and buy the laggards, which can help maintain your desired risk profile and instill disciplined buying low/selling high.

Fees matter -- a lot. Expense ratios and other fees eat into returns over time, often quietly.

Exchange-traded funds (ETFs) are one of the most common building blocks for beginner investors. They were created as a way to combine the diversification of mutual funds with the trading flexibility of stocks.

When people first begin investing they often ask: 'What's the real difference between stocks and bonds?' A clear analogy is helpful: owning a stock is like owning a slice of a business -- you share in its profits and risks -- while owning a bond is like lending money to that business or a government and getting interest in return. Stocks typically offer higher potential returns but with more price volatility.

Dividends are one way stocks return money to shareholders: a company can distribute part of its profits as regular cash payments. For many investors dividends provide steady income and can be reinvested to harness compound growth.

Diversification is often recommended to reduce risk, but what does it actually accomplish in practice? Spreading investments across different stocks, bonds, sectors, or geographies means a single company's poor performance has less effect on your overall portfolio. It helps smooth returns because different assets respond differently to the same economic events -- for example, bonds may hold up when stocks fall.

Compound growth is a foundational idea in investing: it means you earn returns not just on your original money but also on the returns that money has already produced. Albert Einstein (often credited informally) and many educators have used compound growth to explain why starting early matters.