What is a DDOS attack?

The server of this blog had just experienced a DDOS attack or Distributed Denial-of-service attack, and thats the reason why we cannot access this blog a couple of hours ago. For those who doesn’t know what is a DDOS attack, here is what I have searched in wikipedia.com and it says:

A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer resource unavailable to its intended users. Although the means to carry out, motives for, and targets of a DoS attack may vary, it generally consists of the concerted efforts of a person or people to prevent an Internet site or service from functioning efficiently or at all, temporarily or indefinitely. Perpetrators of DoS attacks typically target sites or services hosted on high-profile web servers such as banks, credit card payment gateways, and even root nameservers. The term is generally used with regards to computer networks, but is not limited to this field, for example, it is also used in reference to CPU resource management.

I don’t know the reason behind of this attack but surely it has decreased the traffic that this blog. And I hope I could recover it.