How can messaging service be used to transfer data server to server?

People have told me that the best way to transfer/send data from one server to another is to use messaging service but I don't quite understand it. Publishing and Subscribing I don't see how that can send data at all. If someone could explain messaging service as well as how to use it to transfer data that would be appreciated.

Here's an example, where one server is trying to find a server that needs more players This script is looking for a server

local placeId = --PlaceId
local MS = game:GetService('MessagingService')
local topic = 'FindAvailableServer'

--Some other code here

local function Start()
    debounce = true

    script.Parent.StartLabel.Text = 'Searching for Server...'

    MS:PublishAsync(topic, 'Player-'..game.Players.LocalPlayer.UserId) --Send out async with a channel to send it back
	
    local past = time()
    local GameFound = nil
    local Connection = MS:SubscribeAsync('Player-'..game.Players.LocalPlayer.UserId, function(message) --Listen in that channel
        GameFound = message
    end)
	repeat wait() until GameFound ~= nil or time() - past > 10 --Wait till 10 seconds have elapsed or a game is found
    Connection:Disconnect()
    if not GameFound then
        script.Parent.StartLabel.Text = 'Unable to locate a server. Creating one...'
        --Create a new server
        script.Parent.StartLabel.Text = 'Server Created! Teleporting...'
	--Teleport player to the server
    else
        script.Parent.StartLabel.Text = 'Server Located! Teleporting...'
        tps:TeleportToPlaceInstance(placeId, GameFound, game.Players.LocalPlayer) --Teleport player to that server
    end

    debounce = false
end

--Some more code here

This is the server checking for any requests

local MS = game:GetService('MessagingService')
local topic = 'FindAvailableServer'

while true do
	wait()
	local connected = false
	local Connection = MS:SubscribeAsync(topic, function(message) --Listen
		connected = true
		if workspace.GameInProgress.Value then
			MS:PublishAsync(message, nil) --Send back on the channel nil (Not available)
		else
			MS:PublishAsync(message, game.JobId)--Send back on the channel nil (available)
		end 
	end)
	repeat wait() until connected --Wait till connected to disconnect 
	Connection:Disconnect()
end

I'm pretty sure this is how the messaging service works. I hope this helps!