Can a DDoS attack reveal any information or be used to mount a hack? My understanding is that the whole point of DDoS or DoS is to consume all of the resources/overload the server causing it to crash. And that being the only reason to do a DDoS. 

I have heard that DDoS is used to get information. Is that true or totally false?

A DDoS will certainly give an attacker information about response times, load capability and routing.

It may also give information about how incidents are handled internally and externally, as well as how they are reported to the public.

But this is not what the main uses are.

Generally the two key reasons for DDoS are to:


take a service or website offline
distract from a wider attack, exploit or intrusion


The first is well known, very popular, and is relatively straightforward to carry out, with the only defence against a large attack being a high volume DDoS mitigation service.

The second is more rarely used, but is being seen as a part of an attacker's toolset. Loading the incident response team can make it harder for them to detect an intrusion, can hide the real reason for the attack, and can hide evidence of an intrusion in amongst large numbers of log entries from the DDoS.
