A Bear Market is a prolonged period in which investment prices fall, accompanied by widespread pessimism. Investors anticipating further losses are often motivated to sell, with negative sentiment feeding on itself in a vicious circle.

It is not a simple decline, but a substantial drop in the prices of the majority of stocks over a defined period of time. According to The Vanguard Group, "While there’s no agreed-upon definition of a bear market, one generally accepted measure is a price decline of 20% or more over at least a two-month period."

Dollar Cost Averaging is the act of buying the same dollar amount of a stock each month. This allows you to buy more shares when the stock's price is low and fewer shares when it is high. It can often be more successful than buying the same number of shares each month.

A mutual fund is a professionally managed pool of money from many investors and that is invested it in stocks, bonds, short-term money market instruments, and/or other securities. The mutual fund will have a fund manager that trades the pooled money on a regular basis. As of early 2008, the worldwide value of all mutual funds totals more than $26 trillion.

Buying and selling the same stock during one day. All positions are usually closed before the market close of the trading day.

Short selling is the act of selling stock that you don't own at a high price by borrowing it from a brokerage and then buying it back at a lower price in the future. The hope is that the stock price will drop in value and a profit can be made. This is an advanced technique that has strict requirements and higher risks.

Stock is a piece of ownership of a company. When a company needs to acquire extra money to help grow the business, they can sell some or all of the ownership of the company in the form of stocks. So if you were to buy 100% of a company's stock, you would own the whole company. If you own enough stock you also have some decision-making power within the company. Buying stock is the most popular form of investing.

Simple Answer, it stands for Pink Sheets. It comes from the pink paper on which the National Quotation Bureau originally printed information on OTC stocks. Comparable information on OTC bonds was printed on yellow paper.

From the Houghton Miflin Company: The registered name for a privately owned company that operates a centralized quotation service that collects and distributes market maker quotations for securities traded in the over-the-counter market. The service is named for the color of the sheets on which the National Quotation Bureau distributed bid and ask quotations for OTC securities. In 1999 Pink Sheets introduced its Electronic Quotation Service, which provides real-time quotes for OTC equities and bonds.

This video on FeedTheBull has a great explanation of what short selling is, http://www.feedthebull.com/video/thrasher-university-what-short-selling.