*nod*....they do differ, both in how the process searches, and in the way you address them....the links I noted above lead directly to some detailed explanations...

(I use basically two most of the time...Google and AlltheWeb(FastSearch) which has almost as many web pages indexed, but has what I think is a better image search facility.)

If you want to REALLY play, download Copernic a program which sets on your computer and can be told which search engines to look at and how to organize the results..etc. Amazing tool!