There are no stupid questions. Clustering allows you to do more jobs at once than you could do with a single machine of the same power. It allows for redundancy if you set things up in such a way that if one hardware components fails another takes over. It can allow for better isolation between processes for security reasons than what a process isolated from another process on the same machine can give you. And many other reasons besides, so clustering is a technique that can give you many different benefits.

But...

There is a price to pay. Clustering isn't easy, convenient or without overhead. As soon as you cross the boundaries of what a single machine can give everything suddenly has a price, either in terms of latency, throughput, complexity or loss of control. Clustering software tries to hide some of this but under the hood these will always be there.

Here are some good hints about what limitations you are operating under no matter how good your distributed environment:

https://en.wikipedia.org/wiki/Fallacies_of_distributed_compu...

https://en.wikipedia.org/wiki/Amdahl%27s_law