What are the differences between ncat, nc and netcat?

I'm not sure about when to use nc, netcat or ncat. If one is the deprecated version of another? If one is only available on one distribution? If it is the same command but with different names? In fact I'm a bit confused. My question comes from wanting to do a network speed test between two CentOS 7 servers. I came across several examples using nc and dd but not many using netcat or ncat. Could someone clarify this for me please?