Loading screen in games?

local something = ...something here...
if something ~= nil then
script goes here
end

I see that there are quite a few Roblox games with loading screens, but do those loading screens actually do anything, or are they just there for show? Is there a way to detect if assets have actually loaded or anyway to have a loading screen function in anyway besides just being there to make the game's intro look nice? Can someone link me to some resources that teach this sort of thing if it is possible?

I know that this waits until something is there to continue, but even if the game sees that a decal or sound is there, doesn't mean that the texture or soundId will actually load, so it doesn't really mean that the loading screen does anything... Any ideas or resources I can see? Please help!