What is a Search Engine?
A search engine is a tool that allows users to search for data and information via the World Wide Web. The list of contents is returned to a user is known as a search engine results page.
Crawling, & Indexing
A search engine crawler (also known as a web spider or bot) is a piece of software that scans web pages, and collects information for indexing purposes.
Key point: Via non-paid (also known as 'organic search engine results, SEO is the practise of increasing both the quality and amount of website traffic, as well as visibility to your brand.