Here is a brief explanation on Common Shares.

Advantages of owning common shares:

1) A marketable asset
2) Potential for capital appreciation
3) Favourable tax treatment
a) Dividends
b) Capital gains
4) Voting – a say in the affairs of the company
5) Dividend income
6) Limited liability investment

Most suitable for long-term investment (10+ years); hopefully your company doesn’t go under

Problems: can be very volatile (risky) over short periods of time.