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.
At initial stages of business development there several types of potential investors: