1. A method of searching for and providing information about a natural language query having a simple or complex sentence structure, the method comprising: generating a mashup query language having a tree structure in a plurality of levels based on at least one query entity included in a natural language query language via a semantic analysis of the natural language query language; determining whether the plurality of levels are linked through a query entity forming the mashup query language of each of the plurality of levels based on attribute information of the mashup query language; searching for data corresponding to the query entity forming the mashup query language of each of the plurality of levels from a knowledge database based on a result of the determining, and deriving main information and at least one piece of entity information corresponding to the natural language query language from the searched data; and laying out a search result screen comprising the main information and the at least one piece of entity information.