There are different kinds of clusters. If you are interested in the kind of cluster where each node provides load balancing, share the same disks between the cluster nodes, and failover protection then you may be interested in the Red Hat type of high availability cluster.
Here is information on Red Hat clusters on RHEL 6.
There is another kind of cluster that only divides a multi threaded task or several separate tasks between different nodes. This kind of cluster first appeared at NASA and was called Beowulf. These days this kind of cluster can be implemented using more current code under the Open Mosix project. This project was abandoned in 2008.
Microsoft implemented a failover and load balancing cluster.
And, AFAIK Digital Equipment Corporation invented the computer cluster as implemented in their VMS operating system. It has not been matched for versatility, robustitude, (robustitation?)
or ease of administration. In other words there have been attempts to create a computer environment as good as or better than the DEC VMS cluster but IMO none have met that goal.