What are serialized variables?

So serialized variables are the mechanism that we expose to the gameplay programmers to allow them to communicate over the network. The game is built out of entities, entities are built out of components. Components have these serialized variables, which are values that can change over time as the gameplay programmers assign new values to them. Those changed values will get replicated over the network to the equivalent entity on your clients. It will change the value of the serialized variable there as though it's been changed exactly by the server. So it's a remote control over the state of entities in the game.