【急】状态变成了 correspondence was received and review

我是3.27寄出去的 不久状态变成了 case was received。。 刚刚不知为什么状态变成了correspondence was received and USCIS Is Reviewing It. 这是开始审核的意思 还是 别的什么啊？ 我并没有寄任何多余的材料呀。。。