TextureTrials, their use, and how do I use them?

local bc = BrickColor.new("Lavender")

local b = Instance.new("Part")
b.Name = "TTBrick"
b.Parent = game.workspace
b.FormFactor = "Custom"
b.Size = Vector3.new(4, 4, 4)
b.Transparency = 0.5
b.Anchored = true

local tt = Instance.new("TextureTrail")
tt.Parent = b
tt.Color = BrickColor.new("Lime green")
tt.Transparency = 0.5
tt.Visible = true