Can somebody explain DataStore a little better?

I don't quite understand it

local DataStore = game:GetService("DataStoreService"):GetDataStore("Weapon1")
 
game.Players.PlayerAdded:connect(function(player)
	local key = "Weapon1" .. player.userId
	DataStore:GetAsync(key, function(oldValue)
		if oldValue == new then
			--code to give weaoon
		else
		print("weapon not owned")
	end)
end)

Would that work to check if somebody owned a weapon before?

I Love this script and how you made it, Yes. It does work, the problem is... You need to save the weapon to the data store