Best search engine
What is the best search engine ? It depends what are You looking for if privacy and You can consider DuckDuckGo a best search engine, for sure most popular and really counting are Google, Bing and local search engines like yandex in Russia or Baidu in China. They are all based on crawling sites with special bots which pulls data from each website and then they are using the data to depending on the query serve the search results to user.
Search engine traffic
Search engine traffic depends from number queries for the keyword and this of course also depends from how the current search engine is popular and what is it used for. For example search in youtube is also search engine but the content makes it`s traffic totally different than the other search engines.
Search engine marketing
We can divide it for paid marketing and free marketing. To free marketing we can add SEO and maybe content marketing if we don`t think it is a part of SEO. Paid marketing is mainly Adwords and Display.
Search engine optimization
Search engine optimization means actions to improve website positions in search results. We wrote about it in more details here what is seo
Search engine submission service
Some companies offer submission services to different search engines which is a bit a rip of because it is free for all people , just try to google : add url to Google, add url to Yahoo etc.