I have heard there are several types of tokens on the market. What is the main difference?

You are absolutely correct, there are several types of tokens. Here are short explanations for them all:
 

• Utility token: gives you a right to buy product/use service of token issuer

• Cryptocurrency: a coin that is meant to be used for payments/transactions in a specific network

• Stock tokens: tokens that are issued following all rights of securities, usually projects guarantee to pay out % of profit or revenue to tokenholders

• Bonds tokens: token that gives the owner a right for an announced plan of payments (really close to a normal bond)

 
 
More about it here: https://medium.com/digital-finance/types-of-tokens-affc38d254e5