Is webcrawler a search engine?
No a web crawler is definitely not a search engine. It is a automated software algorithm that roams around the internet (crawls) the pages on www. It goes from one page to another using links present on the pages. It then keeps a copy of the HTML output of the pages in the huge databases maintained by the search engine companies. On the other hand a search engine is an internet application where you provide some keywords and based on these inputs it returns some results by searching the same copies of the web pages crawled by the crawlers before. Most of them go by matching the text content with your keywords while some also work on tags.
