A stock is a share in the ownership of a single company, representing a small fraction of the company’s total value. On the other hand, a mutual fund is a collection of stocks, bonds or other assets owned by many investors and managed by a professional investment company. The idea behind a mutual fund is to pool the money of many investors to create a diversified portfolio that can be managed by experienced investment professionals. So, the main difference is that a stock represents a single company, while a mutual fund represents a collection of multiple assets.