"snowball effect" 的定义和意义

What is the origin of the idiom "snowball effect" and when to use it?

The idiom "snowball effect" is derived from the literal concept of a snowball rolling down a hill, gradually picking up more snow and increasing in size as it goes. In a figurative sense, it is sued to signify a situation in which a small action or event triggers a chain reaction, causing an issue or situation to grow rapidly or become more significant.