Not exactly, google uses a 'crawler' that follows links and behaves much more like a human (ie viewing 1 page at at time) automated downloaders tend to open several simultanious connections to a server at the same time and download as much content as possible. In addition search engines respect the file robots.txt which may contain a list of files to be indexed, and files not to be indexed. (linuxforums.org has one,
here should you want to see one) its a fine line, but in the end, the only *serious* difference that I know is google does this in moderation, and behaves more like a fast reader would as opposed to a DOS style script which has no reguards for moderation.