What is the difference between Debris:AddItem and Destroy()?

Well, there is 2 ways, of destroying a brick

example: you want to destroy a brick inside workspace, the most easiest way is you can call the function :Destroy(), but for example, if you want a script that runs anyway without having to wait, then you can use :AddItem(), because its accept 2 arguments, example game:GetService("Debris"):AddItem(game.Workspace.Part,3), then the script will not yield but continues with the next code, so it does not yield for the part disappearing, but in the way we have :Destroy() and if you do like this

print("Deleting part in workspace, and waiting 3 seconds")
wait(3)
game.Workspace.Part:Destroy()
print("Part was destroyed, but the code was not executed here, it waited for 3 seconds")

additem:

print("Deleting part in workspace and waiting 3 seconds to delete it")
game:GetService("Debris"):AddItem(game.Workspace.Part,3)
print("This code was executed, but the part still have to wait 3 seconds before it gets deleted")

hope i helped

The AddItem should be used if you want a part to gets deleted but the code should still run to next step

Destroy has no delay argument and if you want a script to wait until it is destroyed, then use like

print("Waiting 3 seconds and then destroying the brick")
wait(3)
game.Workspace.Part:Destroy()
print([[This code needed to wait, but this line got executed after the "wait" line]])