I heard some people talking about how they had a 3 gigabyte per second drddosser. That sounds all fine and dandy, but what can that actually do? Could it take down a website? To what extent?
Unfortunately your question is lacking some details, but I can give you some food for thought on this that will help put this in context. First of all there are different protocols that could be used for an attack such as ICMP, or UDP or TCP. Without knowing more about the target or type of traffic generated it's hard to truly predict what impact it would have.
Having to assume a generic type of traffic, this attack would effectively use up 3 Gbps of bandwidth. Depending on the server's configuration, resources, etc. this could be enough. If the server is connected to a 1 Gbps ethernet link (a typical configuration) it may actually be overloaded by this bandwidth. There are many mitigations for this that can be performed, again depending on the type of traffic. Most cloud providers would detect this traffic and mitigate it after a short amount of time, perhaps even automatically. If you want to comment on my answer with more specifics I'd be happy to update my answer with more details.