Scripts make your game run smoother and faster, right?

I'm not sure what you mean by that but if a script lags or not is dependent by its efficiency.

Most of the time, even if the script is inefficient, it won't lag.

A script is something that allows the stillness of a game come to life. It can be used for almost anything you can imagine or want in a game-verse. They are used in MOST if not ALL popular games or popular games in the past. Scripts are a vital as GUI's.

How good a script is is determined by its efficiency only in my book.

Bad script:

script.Parent.TextTransparency = 0.1
wait(0.1)
script.Parent.TextTransparency = 0.2
wait(0.1)
script.Parent.TextTransparency = 0.3
wait(0.1)
script.Parent.TextTransparency = 0.4
wait(0.1)
script.Parent.TextTransparency = 0.5
wait(0.1)
script.Parent.TextTransparency = 0.6
wait(0.1)
script.Parent.TextTransparency = 0.7
wait(0.1)
script.Parent.TextTransparency = 0.8
wait(0.1)
script.Parent.TextTransparency = 0.9
wait(0.1)
script.Parent.TextTransparency = 1

Good Script:

for i = 0,1,.1 do
    script.Parent.Transparency = 1 - i
    wait(.1)
end

If you don't know how to script a good place to start is Youtube - Peasfactory and use the ROBLOX Wiki to relook up anything you forget because thats basically all I use it for XD.