what是问什么东西或事物的疑问词,this是这个的意思,what'sthis就是what is this,只不过what is缩写成what's,is是be动词,是的意思。比如she is a teacher,她是一个老师,整句话翻译就是这个(this)是(is)什么(what)。
"What'sthat? " He went across the fire and foundthatit was a red stone.───肯看到她正凝视着手中的什么东西。“那是什么?”他跨过火堆,发现那是块红色的石头。