In addition to your own investment, you borrowed money from your broker to purchase shares of a stock- Your broker called to tell you that the price of your stock has fallen and you now need to contribute more of your own money to keep the account at the minimum level- This is termed a(n)

There are 4 main types of investments:
Shares. 
Property. ...
Cash.
Fixed interest.

Often, people take investment to be about buying and selling shares only. You buy a stock or bond, with the hope that its value will increase over time. Although investing comes with the risk of losing money, should a stock or bond decrease in value, it also has the potential for greater returns than you'd receive by putting your money in a bank account. Thus the common clubbing of investment and share investing.