我将一个文档插入到一个mongoDB集合中，并收到消息WriteResult({"nInserted":1})db.myColl1.insert({title:'MongoDBOverview',description:'MongoDBisnosqldatabase',by:'tutorialspoint',url:'http://www.tutorialspoint.com',tags:['mongodb','database','NoSQL'],likes:100})WriteResult({"nInserted":1})WriteResult({"nInserted":1})是什