Funds are financial products in which funds collected for specific purposes are managed by asset management companies on behalf of investors.
It is not easy to decide where and how much to invest in stocks. When you join a fund recruited by a financial institution, fund managers, who are investment experts, invest the money in several places.

ex. It's 1 dollar for 1 bread and 2 dollars for 4 breads. But I can't buy a loaf of bread because I only have 50 cents.
But if I bring 3 friends and 4 people including me pay 50 cents each, I can buy 1 bread, right? (In this way raising money is called a fund)