Example

-- in this script, i made a fireball. this is a local script, it will fireserver a script in the serverscriptservice.

--–//Services\–
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local UserInputService = game:GetService("UserInputService")

--– Variables----
local player = game.Players.LocalPlayer
local Character = player.Character or player.CharacterAdded:Wait()
local Remote = ReplicatedStorage.Fire.Fireballevent
local Mouse = player:GetMouse()

--–//Settings\–
local Debounce = true
local Key = 'Q'

UserInputService.InputBegan:Connect(function(Input , IsTyping)
	if IsTyping then return end
	local KeyPressed = Input.KeyCode
	if KeyPressed == Enum.KeyCode[Key] and Debounce and CUA4 == true and Character then
		Debounce = false
		Remote:FireServer(Mouse.Hit)
		print "Fireserver"
		wait(.1)
		Debounce = true
	end

end)

-- this is the script in serverscriptservice:

--–//Services\–
local ReplicatedStorage = game:GetService("ReplicatedStorage")

--– Variables----
local Remote = ReplicatedStorage.Fire.Fireballevent

--–//Settings\–
local Damage = 30

Remote.OnServerEvent:Connect(function(plr, Mouse)
	local Character = plr.Character or plr.CharacterAdded:Wait()

	local Part = Instance.new("Part")
	Part.Shape = Enum.PartType.Ball
	Part.Anchored = true
	Part.CanCollide = false
	Part.Transparency = 0.5
	Part.Color = Color3.fromRGB(255,0,0)
	Part.Material = Enum.Material.Neon
	Part.Size = Vector3.new(3,3,3)
	Part.Name = "FireBall"
	Part.CFrame = Character.HumanoidRootPart.CFrame *CFrame.new (0,10,0)
	Part.Parent = workspace

	local tweenService = game:GetService("TweenService")


	local tweeningInformation = TweenInfo.new(

		3,
		Enum.EasingStyle.Linear,
		Enum.EasingDirection.Out,
		0,
		false,
		0
	)

	local partProperties = {
		Size = Vector3.new(10,10,10);
		Transparency = math.random(0,1)
	}


	local Tween = tweenService:Create(Part, tweeningInformation, partProperties)
	Tween:Play()

	wait(3)

	Part.Anchored = false


	local BodyVelocity = Instance.new("BodyVelocity")
	BodyVelocity.MaxForce = Vector3.new(math.huge, math.huge, math.huge)
	BodyVelocity.Velocity = Mouse.lookVector*100
	BodyVelocity.Parent = Part
	local Debounce = true

	Part.Touched:Connect(function(h)

			local tweenService = game:GetService("TweenService")


			local tweeningInformation = TweenInfo.new(

				1,
				Enum.EasingStyle.Linear,
				Enum.EasingDirection.Out,
				0,
				false,
				0
			)

			local partProperties = {
				Size = Vector3.new(50,50,50);
				CFrame = h.Parent.HumanoidRootPart.CFrame;
			    CFrame = h.CFrame;
				Transparency = 1
			}
			BodyVelocity:Destroy()
			Part.Anchored = true
		Part.CFrame = h.Parent.HumanoidRootPart.CFrame

			local Tween = tweenService:Create(Part,tweeningInformation,partProperties)
			Tween:Play()






	end)
end)


that was the fireball script..