An investor is a party that makes an investment into one or more categories of assets --- equity, debt securities, real estate, currency, commodity, derivatives such as put and call options, etc. --- with the objective of making a profit. This definition makes no distinction between those in the primary and secondary markets. That is, someone who provides a business with capital and someone who buys a stock are both investors. Since those in the secondary market are considered investors, speculators are also investors. According to this definition there is no difference.

http://en.wikipedia.org/wiki/Investor