How would you use a for loop?

You could use this for(sort of) smooth part interpolation.

for q=1,360 do --do 360 times
	part.CFrame = part.CFrame*CFrame.Angles(math.rad(1),0,0) --will pin it around smooooothly
end

You could use it for fading.

part = game.Workspace.Baseplate

for q=0,1,.01 do
	part.Transparency = q
end

And like Sporkyz said, search through tables, and repeat a certain number of times.

Sporkyz actually deleted his answer though.

You could use it for random map generation. Or to do something to all the players in game or parts in a model.

for q=1,#game.Players:GetChildren() do
	local player = game.Players:GetChildren()[q]
	player:Kick("Bwahahahaha! I hackified you!") --good to kick all the players
end

for i,v in pairs(game.Workspace.Model:GetChildren()) do wait()
	v.Color = Color3.new(math.random(0,255)/255,math.random(0,255)/255,math.random(0,255)/255)
--color all the parts randomly
end