How could I make a part snap to grid? [closed]

I already have the moving part of the script but now I need to make the part snap to grid which the part in this case target:

local plr = game.Players.LocalPlayer
local mouse = plr:GetMouse()
local target = nil
local down = nil
local plr = game.Players.LocalPlayer

function gettarget()
    if mouse.Target ~= nil then
        if mouse.Target.Parent == game.Workspace[plr.Name .. "w"] then
            target = mouse.Target
            mouse.TargetFilter = target
            down = true
        end
    end
end
mouse.Button1Down:connect(gettarget)

function move()
    if down == true then
        if target ~= nil then
            local PosX,PosY,PosZ = mouse.Hit.X,mouse.Hit.Y,mouse.Hit.Z
            target.Position = Vector3.new(PosX,PosY,PosZ)
        end
    end
end
mouse.Move:connect(move)

function releasetarget()
    down = false
    target = nil
    mouse.TargetFilter = nil
end
mouse.Button1Up:connect(releasetarget)

Also could you please explain to me how the snapping works?