Complex Search is a search that is complex in nature. It is using multiple search settings to query a database. If one cant find something on normal search tools one uses the complex search tool.
A complex search is when you are searching for things so closely related that they are almost insitinguishable. It is when you are using multipe search settings to find answers.
A complex search can mean many different things.The common thing it refers to is a search that is complex in nature.For instance if you want to search the meaning of a word that would be a simple search, but if you are doing research for a topic you are writing a paper on that would be a complex search.