Friend, robot.txt is a simple text file through which we can instruct the search engine which page have to be cache or not.

Robot.txt a important server file which define that which are be crawl by search engine crawler or not. if your do not want some links or page or not want that be crawl by search engine then we can be control that by robot. txt. its so important for seo.
Thanks

Is it a good idea to move up in search results for the robots.txt to just scan your home page?

hello friend, robots.txt is a text file resides in root DIR of website. It allow us to block complete or partial website portion. Make Sure to use a correct syntax of robots.txt. Almost all major search engines like Google, Bing, http://www.oko69.com ...... respect the presence of robots.txt.

thanks