That is the same thing with different names, correct?
I have always used the names interchangeably... EtherChannel is like the feature name, but the syntax is "port-channel", int po1, etc.
Strictly speaking no.
etherchannel = a technology allows the bundling of multiple individual physical links into one logical link.
portchannel = the Cisco representation of the logical interface. So when you configure an etherchannel on a Cisco device a port-channel interface represents th logical link.