how to make a part spawn at your mouse cursor when you click?

How do I make a part spawn at my mouse cursor when I click? And how do I make it despawn?

When asking a question please provide previous attempts that you have tried so you don't ask a "Make me this" type of question, anyways, since this is a simple question I'll answer it.

What you'll need are 3 things: A RemoteEvent, a LocalScript, and a ServerScript

First of all, let's make a RemoteEvent in ReplicatedStorage and name it GeneratePart

Secondly, let's have our LocalScript, which I had placed in StarterPlayerScripts

This script will fire the RemoteEvent so that way other players will be able to see the parts being generated, you should have this inside of it:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

local RP = game:GetService("ReplicatedStorage")
local Event = RP:WaitForChild("GeneratePart")

mouse.Button1Down:connect(function()
	Event:FireServer(mouse.Hit.p)
end)

Finally, put the ServerScript in ServerScriptService, which will respond to the Event being fired, and put in the following:

local RP = game:GetService("ReplicatedStorage")

local Event = RP:WaitForChild("GeneratePart")

local DespawnTime = 1

Event.OnServerEvent:connect(function(player, Pos)
	local Part = Instance.new("Part",workspace)
	Part.Position = Pos
	wait(DespawnTime)
	Part:Destroy()
end)