something通常用于肯定句,anything通常用于否定句或疑问句.
例如：
There is something in the box.（肯定句）
There isn’t anything in the box.(否定句)
Is there anything in the box?(疑问句)
Nothing 在意义上等于 not anything.
例如：I know nothing about it.(=I don’t know anything about it ）我对此事一无所知.
everything :
1.一切事物；每样事物：
This shop sells everything needed for camping.这家商店出售一切露营用具.
Tell me everything about it.告诉我这件事情的始末.
2.最重要的事；
Money is everything to him.金钱对他比什么都重要.
She`s beautiful,I gree,but beauty is not everything.我同意她是美丽的,但美并不是最重要的.