Mutual funds work by pooling your money with the money of other investors and investing it in a portfolio of other assets (e.g., stocks, bonds). managed by a fund manager, who picks all the investments in the portfolio. As the value of the fund increases, so does the amount you invested.
The act of adding money to a mutual fund is called subscribing. When you subscribe, you own unit/s of the fund that you can redeem when you want to get your money back to your GCash wallet.