I am learning about the Ethereum network and I think I have a general understanding of how things work. One thing I am unsure about is the precise mechanism by which an external user that is not part of the network (not a node/client) communicates with a network node. What I don't understand is the point of entry to the network.
For example, if a random computer with an internet connection wants to send a simple JSON-RPC read request to the Ethereum network to get a transaction by its hash without using a node provider like Alchemy, Infura, etc. How does this communication happen exactly? Is the request received by one node or many nodes? What decides which nodes in the network receive the request?