I am creating a website and I notice that all the wbsite that I looked at they all had a preloader. Do I really need a preloader on the website? If so how do I use it?

I would put a preloader up if the site takes some time to load. You don't want
people leaving the site. At least with a preloader they can look at something.
My opinion....use a preloader.
If you don't know how to make a preloader just do a search on the forum as it
is probably one of the top 5 questions asked on here. There is a ton of
tutorials if you want to search for them as well.