Volatility is a measure of dispersion. It describes the degree of price fluctuation over a specific period.
Cryptocurrency is considered volatile if its price changes significantly within a day. The volatility of a coin is higher when the difference between the highest and lowest prices is big during a specific period.
The dynamic nature of cryptocurrencies gives the potential to benefit from price changes. Meanwhile, you need to understand the risks involved as the market moves quickly and can change the direction against your position/order.