There are two main types of accounts: cash accounts and margin accounts. There are advantages and disadvantages for each and we will examine each in turn.
Cash accounts are the simpler of the two. In this you deposit an amount of money and can purchase stocks up to the amount deposited. The amount you can lose is just the amount of cash in the account. So if you deposit $100, the most than can be lost is $100. If we look at a more reasonable case, if you holding gain $10 or 10% and by the same token it declines $5 the return is a negative 5%. These accounts can be opened with relatively little money some as low as $500.
Margin accounts offer a wide range of strategies as you can borrow money from the broker. The margin account offers leverage which magnifies the gains and losses and also the risk. Since margin is typically equal to the amount of equity a 10% change in the market produces a 20% change your equity. Margin accounts also offer a wider range of strategies but you are also paying interest on the amount borrowed which will reduce the return. The margin account requires more money, typically a minimum of $2000.
Much of the seeming complexity about accounts arises from tax advantaged (or tax deferred) structures. We will discuss these elsewhere.
Which type of account is right for you? That depends upon your available cash that is on hand, the amount of money that you are willing to potentially lose and you comfort level.