After-hours trading, also known as extended-hours trading, refers to trading that occurs outside of regular trading hours. Regular trading hours for stocks traded on exchanges and certain other markets are from 9:30 a.m. to 4:00 p.m. Eastern Time. After-hours trading sessions may occur before or after regular trading hours. The duration of after-hours trading sessions varies between markets and trading venues. Investors should contact their brokerage firms to determine if and when after-hours trading sessions are available.

The term "bid" refers to the highest price a buyer will pay to buy a specified number of shares of a stock at any given time.  The term ask refers to the lowest price at which a seller will sell the stock.

The bid price will almost always be lower than the ask or “offer,” price.  The difference between the bid price and the ask price is called the "spread."

The total amount of money being borrowed or lent; the initial amount of money invested.

A company's P/E ratio is a way of gauging whether the stock price is high or low compared to the past or to other companies. The ratio is calculated by dividing the current stock price by the current earnings per share. Earnings per share are calculated by dividing the earnings for the past 12 months by the number of common shares outstanding.

Market capitalization is the value of a corporation determined by multiplying the current public market price of one share of the corporation by the number of total outstanding shares.

If you buy on margin and the value of your securities declines, your brokerage firm can require you to deposit cash or securities to your account immediately, or sell any of the securities in your account to cover any shortfall, without informing you in advance. The brokerage firm decides which of your securities to sell. Even if the brokerage firm notifies you that you have a certain number of days to cover the shortfall, it still may sell your securities before then. A brokerage firm may at any time change the threshold at which customers are subject to a margin call.

A limit order is an order to buy or sell a security at a specific price. A buy limit order can only be executed at the limit price or lower, and a sell limit order can only be executed at the limit price or higher.

A “margin account” is a type of brokerage account in which the broker-dealer lends the investor cash, using the account as collateral, to purchase securities.  Margin increases investors’ purchasing power, but also exposes investors to the potential for larger losses.

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An amount owed to a person or organization for borrowed funds. Loans, notes, bonds, and mortgages are forms of debt. These different forms all call for borrowers to pay back the amount they owe, typically with interest, by a specific date, which is set forth in the repayment terms.

To engage in any activity in which money is put at risk for the purpose of making a profit.