Cryptocurrency is like having an imaginative money somewhere but this money can be turned into real money. Like buying stocks for few cents, the stocks are virtual-like and you monitor their growths. You buy it with the hope that it will increase one day so that you can sell it for profit. Cryptocurrency is like that too. You exchange fiat (currency) with the virtual money and hope it increases so that you can sell.
Sometimes you follow 'experts' view on which tokens or coins to buy so that you can make profit and minimise possible loss.