Shares

Common Stock

Shares are normally traded in lots of 100 Investors

Investors like to purchase shares in multiples of 100 share blocks. A 100 share block is referred to as a "round lot".
The people that own the ordinary shares of a company have the power to control the company if they have a majority. Usually each ordinary share is equivalent to one vote. Shareholders can influence how a company is run by voting in (or dismissing ( the directors. Major company decisions require 75% of the shareholders voting in favour. Most of the time the shareholders vote the way the directors advise them to.

Owning shares represent ownership of the company and a claim on the company's earnings and assets.

Different Classes

Companies can issue different classes of common stock
The main reason is to retain the voting power within a certain group of shaeholders.
One class is given perhaps 10 votes per share while the other/majority class are given 1 vote per share.

Share Prices

Share prices are quoted in "points" where each point is equal to $1. Fractions are normally reduced to 1/16th of a point and the expressed in there lowest common factor (ie 8/16th = 1/2)

Share Prices are affected by the following:

Interest rate movements
The overall share price movement in the market
Dividend payment to the shareholders

Company's performance in terms of profitability
Company's performance in terms of potential profitability
Changes to the structure of the company
Changes to the senior management