In today's financial markets, the distinction between stocks and shares has been somewhat blurred. Generally, these words are used interchangeably to refer to the pieces of paper that denote ownership in a particular company, called stock certificates. However, the difference between the two words comes from the context in which they are used.
For example, "stock" is a general term used to describe the ownership certificates of any company, in general, and "shares" refers to a the ownership certificates of a particular company. So, if investors say they own stocks, they are generally referring to their overall ownership in one or more companies. Technically, if someone says that they own shares - the question then becomes - shares in what company?
Bottom line, stocks and shares are the same thing.