DoS: a DoS Attack is a Denial of Service attack- it involves using one computer / Internet connection to flood a server with packets (TCP / UDP) - The Objective of this attack is to 'overload' the servers bandwidth / other resources, This will cause a Denial of Service to anyone else that tries to use the server for whatever reason (HTTP [Website]).etc - hence the name Denial of Service Attack.
DDoS: Yes, There IS a difference- a DDoS Attack (or Distributed Denial of Service Attack) is pretty much the same as a DoS- but the difference in results is massive; as its name suggests the DDoS attack is executed using a distributed computing method often referred to as a 'botnet army', the creation process of which involves infecting computers with a form of malware that gives the botnet owner access to the computer somewhat- this cold be anything from simply using the computers connection to flood to total control of the computer - these attacks affect the victims computer -> server more than a regular DoS- because multiple connections are being used against ONE connection, Think of it like a fight, if there is a 1-on-1 fight; the chance of the good guy winning is far higher than if he was being beaten up by severalthousand tough-guys :)
