What Is a Stock Index?

An index is a reference measure

A stock index summarizes a selected group of companies according to its methodology. The index name identifies a reference measure, not a directly owned share of that basket.

The traded contract matters

Exposure can be provided through different products with their own contract units, price increments, hours and financing. A public display name such as NASDAQ 100 can map to a broker-specific symbol. Confirm the current contract and its conditions before calculating a trade.

Leverage

Leverage allows market exposure to exceed the margin posted. It magnifies changes in equity relative to that margin and does not reduce the economic risk of a position. Set size from a risk budget rather than maximum buying power.

Example

A $10,000 notional position at 1:100 illustrative leverage requires about $100 margin, before broker adjustments.

Spread

Spread is the gap between bid and ask. It may widen around news, thin liquidity or session changes. Raw pricing can still involve commissions, swaps and execution costs; a zero quoted spread does not make a trade free.

Example

A one-pip spread on a standard EUR/USD lot is approximately $10 when the quote-to-account rate is one.

Introduction to Risk Management

Define an affordable loss budget, a reasoned exit and a position size before entering. Stops can slip and correlated positions can share the same risk. Include fees and avoid treating any percentage rule as universally appropriate.

Example

An illustrative $2,000 account with a 0.5% risk budget allocates $10 before fees and possible slippage.