What is the debris service??? How do I use it???

Debris is a service that can be used to remove instances without yielding the code.

For example;

local Debris = game:GetService("Debris")
local Part = Instance.new("Part")

Debris:AddItem(Part, 1)

So, in :AddItem it takes in 2 arguments. The instance you want to add, and the lifetime (or basically, the wait time) before it's actually added.

Once the timer has expired (in our example, after 1 second) the part is removed in the same manner is if doing Part:Destroy().

The reason this is useful is because, again, you won't have to yield your code by doing:

local Part = Instance.new("Part")
wait(1)
Part:Destroy()

Instead, we can run code after the Part is added without losing any time in the code.

local Debris = game:GetService("Debris")
local Part = Instance.new("Part")

Debris:AddItem(Part, 10)
--Do other stuff immediately even without waiting 10 seconds
print("Not yielded")
print("Still not yielded")
print("Etc, lul")

Hopefully, this helps! I definitely recommend using it.