A pivotal role, point, or figure in something is one that is very important and affects the success of that thing.
双语例句
例： The elections may prove to be pivotal in Colombia's political history.
这些选举也许会证明其在哥伦比亚政治史上是至关重要的。
例： The Court of Appeal has a pivotal role in the English legal system.
上诉法院在英国法律体系中起关键作用。