A mutual fund is very similar to an in that it is a conglomerate of bundled into one product. Investors pool their cash into one portfolio which is then allocated by a fund manager into different securities.
There are differences from ETFs regarding fee structure and management, however one of the most significant differences for traders is that mutual funds are not tradable during Entry and exit of a mutual fund is only carried out before the open or after the close depending on how the product is managed. The customer also has very little control over the price.