Web site owners use the /robots.txt file to give instructions about their site to web robots. Web Robots (also known as Web Wanderers, Crawlers, or Spiders), are programs that traverse the Web automatically. Search engines such as Google use them to index the web content, spammer use them to scan for email addresses, and they have many other uses. Look at these page for additional info: http://www.robotstxt.org/ http://en.wikipedia.org/wiki/Robots.txt
Do some searches for explanations. That always seems to be the best and fastest way to learn new things on the internet for me.
I was going to ask the same thing, isn't there some benefits and disadvantages in regards to SEO and robots?