introduced by Engle(1982) and Bollerslev(1986), nowadays, models from the G(ARCH) class are the most popular volatility models among practitioners. GARCH models enjoy such popularity because they are capable of describing not only the feature of volatility clustering, but also certain other characteristics of financial time series, such as their pronounced excess kurtosis or fat-tailedness. researcheres don't have the talent as god to give any assumptions on the data which is generated from reality but they give assumptions when they are specifying models to replicate those statistical properties in the data. that's how the G(ARCH) class come from[see Chapter 3,Tsay's Analysis of financial time series for details in G(ARCH) class models].

同样的问题，值得交流