Witness node is what produces blocks and is used to secure the blockchain.
A full node is what is used to handle calls to the blockchain. It hosts the API to allow applications to query the blockchain and to make changes.
Then you have a seed node which is read only to help speed up the network.
Ok that makes sense. Thanks for the info. Is there anywhere where I can go to like a discord channel or some forum where the witnesses interact with each other? I am very interested in becoming a witness, I just can't afford a sizable server at the moment, but I have a few years of unix sysadmin experience both Linux and BSD. I would like to chat to the other witnesses and potentially become one in the future if I can afford a bigger server.