[SOLVED] Calling a function without parenthesis?

Hi there! So I found a script somewhere in the toolbox and decided to see how it is written. However in the script I saw that some functions are called without parenthesis and I don't get how. Can someone explain? Any help appreciated :)

It is a Module Script that looks something like this:

local module = {}

local function disablePlacement(plane) -- Function 1
    if (currentPlane) then
        renderConnection:disconnect()
        renderConnection = nil
        currentPlane = nil
        module.currentPlane = nil
        currentEvent:Destroy()
        currentEvent = nil  

        if (currentTexture) then
            currentTexture:Destroy()
            currentTexture = nil
        end

        for i = 1, #currentObjects do
            local object = currentObjects[i]
            object.model = nil
            currentObjects[i] = nil
        end

        unbindInputs()
    end
end

local function setLoading(plane, isLoading) -- Function 2
    if (plane.loading == isLoading) then
        return
    end

    plane.loading = isLoading

    if (plane == currentPlane) then 
        if (isLoading) then
            for i = 1, #currentObjects do
                setState(currentObjects[i], states.loading)
            end
        else
            for i = 1, #currentObjects do
                setState(currentObjects[i], states.neutral, true)
            end

            obstacleCollision()
        end
    end
end


module.new = function(base, obstacles, grid)
    local plane = {}
    plane.base = base
    plane.obstacles = obstacles
    plane.position = base.Position
    plane.size = base.Size

    if (math.floor(.5 + plane.size.X/grid) % 2 == 0) then
        plane.offsetX = -grid/2
    else
        plane.offsetX = 0
    end

    if (math.floor(.5 + plane.size.Z/grid) % 2 == 0) then
        plane.offsetZ = -grid/2
    else
        plane.offsetZ = 0
    end


    plane.stateEvent = Instance.new("BindableEvent")
    plane.stateChanged = plane.stateEvent.Event 

    plane.grid = grid
    plane.enable = enablePlacement
    plane.disable = disablePlacement -- Calling function 1 without parenthesis??
    plane.rotate = rotate
    plane.place = place
    plane.setLoading = setLoading -- Calling function 2 without parenthesis??

    return plane
end

module.setLoading = setLoading
module.currentPlane = false

return module

NOTE: These are only some parts of the script, not the full version.

Again, any help will be appreciated :)