What does this fire script mean? It is confusing(variables)

lightOnFire is a function.

Functions take in some values, do something with those values, then can choose to output some values.

The values to take in are between the () in the function definition; in this case, it takes in a part.

Thus if I were to call lightOnFire(workspace.Baseplate), lightOnFIre would run with part as workspace.Baseplate.

When you connect lightOnFire to a Touched event with firePart.Touched:connect(lightOnFire), that means "call this function with the part that touhed firePart whenever it gets touched".

Please, PLEASE use a code block. They make this much nicer!

print("Hello world!")

Ok, so moving on. This is a variable. So you can do this!

local Info = "123456"
print("The info is"..Info.."!")
if Info < 1234567 then
    print(Info.." is less than 1234567!")
end

What this will do in the output is say "123456" and "123456 is less than 1234567!" But this is not only used for print and if's statements, it can be used for much more as a debounce, shortcut in scripting, and easy acess to something! Like this

local IsScriptRunning = false -- debounce. A debounce should be used like on clicked and touched functions.

function Clicked()
    if IsScriptRunning == false then
        local IsScriptRunning = true -- Make it impossible to go through the if statement.
        print("Yay it works!")
        local Brick = game.Workspace.Part
        Brick.BrickColor = BrickColor.new("Lime green")
        local IsScriptRunning = false --Makes the function useable.
    end
end

script.Parent.MouseButton1Click:connect(Clicked)

So those were some basic examples, so variubles can also be used as this. And some scripts have lots of variubles, so there not junk. Like in a tycoon script

local Tycoons = {}
local Teams = game:GetService('Teams')
local Settings = require(script.Parent.Settings)
local BC = BrickColor
local Storage = Instance.new('Folder', game.ServerStorage)
Storage.Name = "PlayerMoney"
Instance.new('Model',workspace).Name = "PartStorage" --  parts dropped go in here to be killed >:)

function returnColorTaken(color)
    for i,v in pairs(Teams:GetChildren()) do
        if v:IsA('Team') then
            if v.TeamColor == color then
                return true
            end
        end
    end
    return false
end
--run this first so if there is a 'white' team it is switched over
if not Settings['AutoAssignTeams'] then
    local teamHire = Instance.new('Team', Teams)
    teamHire.TeamColor = BC.new('White')
    teamHire.Name = "For Hire"
end

for i,v in pairs(script.Parent:WaitForChild('Tycoons'):GetChildren()) do
    Tycoons[v.Name] = v:Clone() -- Store the tycoons then make teams depending on the tycoon names
    if returnColorTaken(v.TeamColor) then
        --//Handle duplicate team colors
        local newColor;
        repeat
            wait()
            newColor = BC.Random()
        until returnColorTaken(newColor) == false
        v.TeamColor.Value = newColor
    end
    --Now that there are for sure no duplicates, make your teams
    local NewTeam = Instance.new('Team',Teams)
    NewTeam.Name = v.Name
    NewTeam.TeamColor = v.TeamColor.Value
    if not Settings['AutoAssignTeams'] then
        NewTeam.AutoAssignable = false
    end
    v.PurchaseHandler.Disabled = false
end

function getPlrTycoon(player)
    for i,v in pairs(script.Parent.Tycoons:GetChildren()) do
        if v:IsA("Model") then
            if v.Owner.Value == player then
                return v
            end
        end
    end
    return nil
end

game.Players.PlayerAdded:connect(function(player)
    local plrStats = Instance.new("NumberValue",game.ServerStorage.PlayerMoney)
    plrStats.Name = player.Name
    local isOwner = Instance.new("ObjectValue",plrStats)
    isOwner.Name = "OwnsTycoon"
end)

game.Players.PlayerRemoving:connect(function(player)
    local plrStats = game.ServerStorage.PlayerMoney:FindFirstChild(player.Name)
    if plrStats ~= nil then
        plrStats:Destroy()
    end
    local tycoon = getPlrTycoon(player)
    if tycoon then
        local backup = Tycoons[tycoon.Name]:Clone()
        tycoon:Destroy()
        wait()
        backup.Parent=script.Parent.Tycoons
    end
end)

So yeah, that's how important variubles are.